Monica Ali arrives at a London cafe for our interview wearing an expression of grim resolve, as though readying herself for a minor surgical operation. We both know, before she starts talking, what is causing it.

It is nearly 20 years since Ali, 54, shot to fame with her debut novel, Brick Lane. The book, published in 2003, told the story of Nazneen, a Bangladeshi teenager who arrives in east London for an arranged marriage to Chanu, a windbag twice her age.

It was a literary phenomenon, generating a buzz akin to the one surrounding White Teeth, Zadie Smith's debut, which had come out three years earlier. Ali secured a two-book deal based on the first few chapters and was included in Granta's list of best young authors before the book had even been published.

When it eventually came out Brick Lane had rave reviews. Critics praised her portrayal of an invisible community in the heart of London as "warm, shrewd and hugely readable". It was translated into 26 languages and shortlisted for the Booker prize. Ali, who was catapulted to literary stardom at the age of 35, rode the wave with apparent ease. The book was adapted into a successful film and Ali became a star at international literary festivals. Then things started to go wrong.

Alentejo Blue, her second novel, published in 2006, met middling reviews. As were her next two books, In the Kitchen, about a restaurant manager in a fading city hotel, and Untold Story, an exercise in imagining what might have happened had Princess Diana faked her own death. It was as though reviewers couldn't forgive her for straying so far from Brick Lane. Then there was nothing.

Her new novel, Love Marriage, out next month, is her first in a decade. So the question hanging over us is, where has she been? Haltingly the answer reveals itself.

In 2011 Ali resolved never to write again. "It was a major loss of confidence, I think. It felt too hard to write. I thought, 'I can't do it'," she says. "But then I got really depressed when I wasn't writing. That was really, really hard. It was the only thing I wanted to do. It was the only thing I knew how to do and yet I didn't have the confidence to keep doing it."

She says this briskly, in the manner of someone who is not comfortable with self-pity. "I don't know what writer's block is or means. Maybe you don't have a subject matter or it's a loss of confidence. If that's a writer's block then I had that, but I call it depression."

Ali is a high-achiever — the eldest daughter of an English mother and a Bangladeshi father. She grew up in Bolton, read philosophy, politics and economics at Oxford, married Simon, a management consultant, settled in a leafy corner of south London and had two children before she published Brick Lane.

In the years since, she has busied herself with other things — raising her children, Felix and Shumi, now in their 20s, and doing voluntary work - she is a patron of the charity Hopscotch, which supports women from minority backgrounds. "It's not like I sat around doing nothing, although some days, to be honest, I would get up, take the kids to school and then go back to bed," she says. "But depression is like that and I came out of it."

It's clear that Ali has changed a lot in two decades. The woman who shines out from early interviews is fiercely self-assured. Today I can feel her self-doubt. Was it the critical response to her later books that prompted the breakdown? "It's quite difficult to pin it down. Because it sort of sits alongside being depressed and that does weird things to your analytical thinking. Where does the cycle begin? What's going wrong?" She pauses. "I'm not trying to evade the question. I actually really don't know."

Brick Lane was adapted into a movie in 2007. Photo / Ruby Films

The illness lasted for about three years, she says, and she has spent a lot of time in therapy. She is enthusiastic about transcendental meditation, which focuses on mantras rather than breathing. "There's a kind of woo-woo side, but there's also good scientific evidence about how meditation stimulates certain kinds of brainwaves and has a calming effect. Also, just practically, it works."

It isn't entirely surprising that one of Love Marriage's central strands takes place in the therapist's office. With this novel Ali is back on familiar ground, tackling issues of identity and belonging. It tells the story of Yasmin Ghorami, the 26-year-old daughter of Anisah and Shaokat, an Indian GP and his wife who have settled in Tatton Hill. Yasmin is engaged to Joe Sangster, the coddled only child of Harriet, a controversial feminist thinker who keeps a collection of Indian erotica in her lavish Primrose Hill home. The ensuing culture clash is comical and poignant as the Ghoramis' safe world is blown apart.

"I had a lot of fun writing this book," Ali admits, with a wry smile. Although the title is about love, the book is really about sex. "There are so many things in the book that pivot around sex and fidelity. There's revenge sex, covert incest — not physical incest, but there's a sexual undercurrent to it — there is sexual violence and sexual identity. It is what drives the story. I'm making it sound like I've written Fifty Shades of Grey," she says, laughing. Not quite; but it is a literary love story, just as Brick Lane was.

Ali is well aware of the intellectual snobbery some authors and critics have for love as a theme; in fact she has fun with it in the book. Yasmin suggests to a famous male author who is drunk at a party that love is a worthy theme for a novel. "Women's fiction," he replies. "Only the frivolous and the foolish waste their time with synthetic stories — plots, characters, motives, denouements!' " Ali chuckles. She is arguing the opposite.

The other jab she makes at the literary establishment is a less light-hearted one. At an awards ceremony we meet Nathan Fuller, a young black writer Harriet has taken under her wing. He's dejected that his eco-thriller has been turned down by yet another publishing house; Harriet advises him to write about something "that is a little closer to home"; the implication being that he should write about race. Was that based on her experience? "Your words, not mine," she says, smiling.

With Love Marriage Ali returns to the immigrant experience for the first time since Brick Lane. I'm curious to know why. "A few people have asked me, were you trying to get away from Brick Lane? What would that have been? My ethnicity? No, how could I? Why would I want to?" she asks. "Where I was stupid and naive was thinking that I could write about anything I wanted to write about, that I had as much right to do that as a white male writer."

She had the sense after Brick Lane that critics were disappointed that she was not being "authentic" enough. "But this is authentically me. I am not authentically one narrow thing. It would have been inauthentic of me to try and parlay that into 'Oh this is now my brand'."

Monica Ali's new novel, Love Marriage, which is out next month, is her first in a decade. Photo / Supplied

It's not something she likes talking about. "I'm hesitant to speak about my experience because everything I say sounds like, 'Oh she's got a chip on her shoulder' or, 'It's sour grapes'," she says. "But that was my accumulated sense of it over subsequent books, whether that is right or wrong. It contributed to my own loss of confidence." She pauses. "You can tell I've been in therapy."

Ali's parents met at a dance in the north of England in the mid-60s, when her father had come to study. Her mother followed him when he returned to Dhaka to work as an inspector of technical colleges. They married and had two children, and would probably have remained there had the civil war not broken out in 1971. They came back to England and Joyce's parents were less than happy to see their daughter return with two children under 5 and a husband who couldn't find a job. Relations between the two generations were strained. For a time the Alis ran a knick-knack shop. Later her father took a history degree and then started to teach at the Open University, while her mother became a counsellor.

I ask if any of that internal conflict she portrays so well in both books comes from her own life. She shakes her head. The family weren't religious and rarely went back to Bangladesh. "My father had some Bengali friends but school was English and that's where you want to fit in." She stops herself. "But then fitting in is the opposite of belonging. I just realised I've said 'fitting in' twice, but if you're consciously trying to fit in then you probably don't feel you belong. There's that strand of Yasmin's character in Love Marriage that may come from me." Ali is not someone prone to off-the-cuff observations; her answers are considered and caveated. She loathes the "hot-take mentality".

She is also intellectually rigorous and astute. In 2007 she wrote an essay in response to coverage of an apparent backlash to her book from some in the Bangladeshi community in Brick Lane. She observed a growing obsession with feelings, particularly those of minority groups.

"The protesters say they feel offended. They feel hurt. They feel angry. Whatever their reasons, whether sound or misguided, the one thing it is not possible to argue with is their feelings," she wrote. While she understood the motivations, "I fear it is taking us to a dangerous place, a marketplace of outrage at which more and more buyers and sellers are arriving, shouting their wares and inflating the prices."

"I hate to say I told you so," she says, smiling, when I bring it up. She feels wary about wading back into public life when feelings are so fraught and people seem to be itching to take offence. There are characters in the novel who could be interpreted as representations of white privilege, "but that is not at all how I see them. They have their own issues," she says. This is precisely why it's a good time to have her back. Nuance is one of Ali's greatest skills; she can lay out a character's flaws, self-delusions and inconsistencies and then make you love them anyway. "Empathy is a muscle," she says, "and you have to do some bicep curls."

Read an extract from Monica Ali's Love Marriage

In the Ghorami household sex was never mentioned. If the television was on and a kissing-with-tongues scene threatened the chaste and cardamom-scented home, it was swiftly terminated by a flick of the black box. When Yasmin began her first period, her mother had slipped her a pack of Kotex Maxi pads and murmured instructions not to touch the Qu'ran. This was confusing because Yasmin never touched the Qu'ran anyway, except at the behest of her mother. But it also made sense because menstruation, as she had learned in a biology class, was linked to reproduction. And the dotted-line diagrams in the textbook were, surprisingly yet undeniably, linked to the actors who pushed their tongues into each other's mouths, thus ruining everyone's viewing pleasure.

Now, at the age of twenty-six, Yasmin knew all about sex. The human body had long since yielded its mysteries. She had slept with three men, and was engaged to be married to the third, Joe, a fellow doctor at St Barnabas hospital. Her parents, Shaokat and Anisah, liked Joe because as a doctor he was automatically suitable, and because everyone liked Joe, he was gifted that way. If Anisah longed for her daughter to marry a good Muslim boy it was an opinion she kept to herself.

Yasmin sat cross-legged on her bed, surrounded by medical texts, waiting to be called down for dinner. She should have been studying for yet another exam, but couldn't concentrate. Four books lay open to demonstrate a commitment that she was unable to put into effect. Instead, she leafed through a magazine she'd found discarded on the train. On the cover: Fake Split! Secret Reunion! She's a Wreck! The headlines referred to celebrities, all pictured, only one of whom Yasmin could identify. This dampened her enjoyment only marginally. She preferred, in any case, the stories about 'real people'. The one she had just finished was about a mother-of-three from Doncaster, who had recently discovered that her seven-year-old daughter was not her biological offspring, a mix-up having occurred at the hospital when she was born. The things people go through! And she, Yasmin, had nothing to worry about, and so much to be grateful for.

When tomorrow night was over she'd laugh at herself. It wouldn't be as bad as she imagined. Her parents would meet Joe's mother for the first time. They'd all eat dinner together at her house in Primrose Hill and discuss wedding plans and make polite conversation. Big deal.

The thought of her parents inside that discreetly sumptuous Georgian terrace induced a faint feeling of nausea. She swallowed it down.

- - - - -

The car slowed and Yasmin realised they were on Harriet's street, her father looking for the house. Five minutes to seven. Not as bad as she'd feared.

'Mrs Sangster and Joe, only these two are living here? Very difficult without servants to manage a house like this,' said Ma. She, like Harriet, had grown up in a wealthy household. Only Harriet, however, had inherited family money. 'But it is only Joe and Mrs Sangster, no?'

'No,' said Yasmin. 'I mean, yes.' After the wedding it would only be Harriet. Joe and Yasmin had started looking for a flat already, and they'd move into it straight after the wedding even if there was building work to be done.

Baba parked the Multipla alongside Harriet's classic Jag and gleaming Range Rover. 'Very good,' he said. 'We are here,' he added, as if Yasmin doubted it. 'Well, shall we start to unload?'

Yasmin began gathering the bags.

'Now, wait, one thing – should I ask about the dowry before the dinner or afterwards?' He lifted his eyebrows to assure her he was joking.

'How much are you willing to give, to get me off your hands?' said Yasmin.

'Oh, no, Mini, it is they who have to pay dowry for my daughter. How much?' He pushed his spectacles up, so the thick black frames rested on his forehead while he performed the calculations. 'No, they cannot afford it. My daughter is priceless to me.'

- - - - -

'I despise it,' said Harriet, with cool relish. 'Guilt is the most useless of all the emotions, the most pathetic, the most self-involved. Guilty about work, guilty about exercise, the environment, family, food, alcohol ... And the worst of all is liberal guilt, that shiny badge of righteousness worn with pride by the morally stunted. They didn't like that one bit! I thought, Yes, there's an article to be written and I should be the one to write it!'

'I'm amazed anyone comes to your salons,' said Joe. 'Do you think they'd feel guilty if they stayed at home?' He smiled at his mother and she wrinkled her nose at him.

'They come to be stimulated, darling. I poke them and they love it. And the hors d'oeuvres. Anyway, Shaokat, that's what I'm working on – an article about the horrors of liberal guilt, and I gave it a run round the block with my friends last week.'

Shaokat had enquired about Harriet's 'current projects and engagements'. It was a risky business. But Harriet, as promised, was on best behaviour. (No mention, thus far at least, of the book she was working on with a photographer friend: Harriet interviewing men about their relationship with their penis; the friend taking de-eroticised shots of the appendages.) They sat at the kitchen table, eating Ma's offerings. Harriet had immediately determined they would replace the boring lasagne she had in the oven (don't worry, Joe told Anisah, she didn't make it, she has someone come in for all that).

Anisah, blissed out by the honour, sat quietly. She gazed around the vast and splendid kitchen at the plate-glass doors that opened to the garden, the sofas and rugs, the vaulting skylights and cushioned window seats; the magnificent range cooker, breakfast bar and marble countertops. Reheating and decanting the curries into chinaware, she'd made herself at home amid the gleaming appliances inside the workspace, and freely inspected the offshoot areas – the larder, utility room, cloakroom, and the enclosed side porch where shoes and boots lined up neatly next to the pretty stack of firewood.

'This is very interesting,' said Shaokat. Yasmin fingered her napkin. Why did he talk so slowly? It was painful to hear him. 'Tell me,' he went on, 'what is the horror, why is it so horrible?'

'I don't want to bore you,' cried Harriet, 'we're celebrating!' She poured more wine into Shaokat's glass, although he had hardly taken two sips. 'And there are wedding plans to discuss.' She turned to Anisah and gave her plump hand a squeeze. Without pause she continued, 'The liberal who feels guilty about the social, political or economic order – global or local – who knows that their comfort and ease depend on the blood, sweat and tears of others, is the enemy of change in the world. You know why?'

'We will in a minute,' said Joe.

- - - - -

'We must not impose on you longer,' said Shaokat. 'And you must visit us in our home.'

'It's only half past nine,' said Harriet. 'You can't possibly abscond. We hardly got started on the wedding plans.'

'Actually,' said Yasmin, 'I'm on an early shift tomorrow, so ...' It was probably best to withdraw now while the Ghoramis could get out of Primrose Hill relatively unscathed.

Harriet ignored her. 'I want to get your opinion on something,' she said to Shaokat. Clearly she'd worked out which buttons to press. Shaokat, duly gratified, removed his bifocals in order to concentrate. 'Muslim marriages aren't legally recognised in this country. Why shouldn't they be?' She paused. 'Or Hindu or Sikh or any other religion for that matter. What's your opinion?'

'An interesting question,' said Shaokat. 'There are many angles to consider.' He furrowed his brow. Normal conversation was quite beyond him. He had to deliver his judgements from above.

Ma seemed to want to say something, but when she opened her mouth only a series of clucking sounds came out.

Harriet turned towards her. 'Yes,' she said, as though Ma had managed an intelligible sentence. 'It's a feminist issue because women in this country, Muslim women in particular, are discovering when their marriages break down that they were not, in fact, legally married in the first instance and that they have no rights at all. Why don't we accord the same rights to all communities?'

Where was this going? Yasmin tapped a little rhythm on her placemat to attract Joe's attention. After the exchange about his dad he appeared to have tuned out.

He noticed but misread the message and reached across the table to refill Yasmin's wine glass. 'I agree,' he said. 'Why should you have different rights if you get married in a church?'

Harriet held out her own glass for a top-up. 'People get married in church, and even though they believe in God as much as they believe in Santa Claus, it's legally valid and their rights are protected. But for people who actually believe, who take their vows before Allah, the marriage is worthless in the eyes of society, in the letter of the law. They should be given the same status, that's only fair, there should be equality.'

Harriet, an atheist, was championing the rights of true believers. She could argue anything, any position. Yasmin – despite her sinking feeling – admired the way Harriet's mind darted, her panoramic intellect, her insatiable curiosity. Ma and Baba had a new thought only once a decade. That was probably an overestimate. Their views never changed. Baba had no time for religion and now was the time for him to say so out loud. Come on, Baba! Speak!

'Right, there should be,' said Joe, as though the conversation was entirely theoretical. Perhaps it was. 'But,' he smiled at Yasmin, 'since we're going to a registry office it doesn't affect us, fortunately.'

'But what will your relatives feel,' Harriet lowered her voice conspiratorially, addressing herself to Anisah, 'about having only a registry office marriage? What do you feel about it?'

'One sister is coming from Mumbai,' said Ma. 'Rashida is a lecturer, and she never married. Another sister, Amina, will come from Harrisonburg, Virginia. Amina is devout. Yes, very devout. She married a dentist and they have three children, all grown now but –' with a touch of pride, '– my daughter is the first to make the marriage.'

'How difficult would it be,' said Harriet, 'to secure the services of an imam? If one were required or desired?'

'Baba,' said Yasmin. But Shaokat was staring at the white leather stools lined up beneath the breakfast bar. He was mid-cogitation and would not speak until he was ready.

'No difficulty,' said Anisah.

'Well, I think that's settled then.' Harriet practically sang the words.

'Hang on,' said Joe. 'What did I miss?' Harriet again put her hand on his bicep and he frowned but didn't shrug her off.

'If there are no objections the proposal is to arrange an Islamic ceremony ... there will have to be a civil ceremony too, of course. Shaokat, what's your opinion?'

'My opinion ...' began Shaokat, and Yasmin noticed just then how unnaturally tight against the table he sat, his chair tucked in so close that his torso seemed almost to sit on top of the oak slab. 'My opinion is that my wife is the one you should ask, since she shoulders the burden of faith for the two of us.'

'If Joe is not objecting ...' said Anisah eagerly. Her round cheeks shone with hope.

'Hang on,' said Yasmin. 'What about me?'

'He will decide, isn't it?' said Ma, not looking at Yasmin.

Harriet directed her gaze at her son. 'I'm looking forward to seeing how many impeccable liberals of our acquaintance turn out to be Islamophobes.'

Yasmin slid low in her chair so she could kick Joe's leg under the table. It wasn't easy because he wasn't directly opposite, but she managed to make contact. He squinted at her earnestly, trying to read her mind.

'There are more Islamophobes in India than in the whole of Europe,' said Baba. 'That is why Modi came to power. His greatest achievement in the eyes of many was the pogrom in Gujarat when he was Chief Minister.'

'Don't get me started on Modi,' cried Harriet. 'Yes, Islamophobia is everywhere, but not in this house! Joseph, isn't that right?'

Joe tilted his head, still observing Yasmin. She widened her eyes in desperation.

'It's fine with me,' he said.

'Bravo!' said Harriet. 'Will you, sister, select the imam? Will he be from your local mosque?'

'I pray at home,' said Ma, 'but also I attend sisters' majlis in Croydon every week. It is a sort of bookclub, but for studying the Qu'ran and the Hadith. I will ask Imam Siddiq. Inshallah, he will be most happy.'

'But it's up to Yasmin,' said Joe, finally catching on as Yasmin shook her head. 'Can't have a wedding without a bride.'

They all looked at Yasmin. And now she hesitated.

Joe looked confused. He shrugged an apology. Baba prepared responses to whatever her response might be. Harriet fizzed with determination, as though she might levitate off her chair. Ma pleaded with her eyes.

She would say no, she decided that was best even though it would cause some awkwardness. Better a little awkwardness now than a lot later on.

'When you were a little girl,' said Ma, 'you always said your prayers. Arif was more difficult. But you always said your prayers with me. Every day.' She sniffed and rubbed her nose.

'Yes, Ma,' said Yasmin. There was a risk Ma would begin to sob if she said no.

'Every day,' Ma repeated.

'I said yes, Ma. Yes. It's fine.'

'Yes?'

There was, Yasmin realised, still a chance Ma would succumb to a weeping jag. 'Yes!' she repeated, rather aggressively. 'If Joe doesn't mind.' But it was hopeless now. Joe wouldn't sit there and overrule her. He'd handed her the opportunity to put an end to this and she'd blown it. Now they'd have Imam Siddiq at their wedding, with his big yellow teeth and oiled hair. They'd have to endure him croaking on and on in Arabic and when he'd maxed out on recitations he'd switch to English for the sermon, and that would be worse.

Joe blew her a kiss across the table. Yasmin forced a smile. Ma kissed her on the cheek. Even Shaokat looked pleased, although he had never said a good word about imams in his life. Perhaps he was pleased for Anisah. Or for Harriet, whose plan it had been, after all. Perhaps he was simply glad his daughter had shown herself to be a good daughter, and a compliant daughter-in-law.

'Joe will convert,' Anisah said directly to Harriet, as if the youngsters could now be safely left out of the arrangements. 'But don't worry, it is simple only. Even on the wedding day itself, he can do it. Only he has to say the Shahada, and it is done. La ilaha illa Allah, Muhammad rasoolu Allah.'

'Is it really? It's done with a sentence? Well, Joseph, consider yourself lucky. If you were marrying a Roman Catholic, think what a palaver that would be! A simple sentence, how beautiful, what does it say?'

'There is no true god but God,' said Anisah, 'and Muhammad is his Prophet.'

'You and I,' said Harriet, 'are going to be such good friends.'

Written by: Rosie Kinchen
© The Times of London