It is the first book since his Booker nomination by the self-confessed "slow writer", but one that has already got critics talking about being another contender for some of the most prestigious literary prizes. Toltz is, his publicist had warned me, reluctant in interviews to dwell on losing the ability to walk, but here he is, telling it all very calmly.
"It felt God-awful. I was all alone, but my girlfriend was working nearby, so I called her and she called the ambulance." First there was surgery to stop the internal bleeding that could have cost him his life. "If it had happened a week before, when I had been travelling in Spain, I hate to think what would have happened. Or at night, when I was asleep. I don't think I would have survived."
The doctors told him he had suffered a cervical spinal haemorrhage, bleeding that compresses the spinal cord. It is a rare condition that can strike out of nowhere. And the prognosis? "They said maybe I probably wouldn't walk again, then that I wouldn't walk again, then that they didn't know any more."
It was devastating news. Since graduating, Toltz had been travelling the world, working variously in Canada as a location manager on films such as Kung Fu: The Legend Continues, then in Spain teaching English, before pitching up in Paris with an ambition to be a novelist that had blossomed as a child when he read Roald Dahl. He was there for a month, but returned home to Australia and to a spinal unit in Sydney.
"I got Medivac-ed," he remembers, referring to the Australian television series about emergency doctors. "I had pictured some kind of army carrier with the door opening to rescue me, but in fact I was on a normal commercial flight with a nurse. They put the stretcher on top of six seats in economy, and the little light and air conditioning valve was about 10 centimetres from my face. It was very similar to being in an MRI scanner - only for 30 hours."
He laughs at the memory. Toltz writes dark, dark comedy - Quicksand has been hailed in Britain by one early newspaper reviewer as "the funniest book I've read in the past 12 months" - and that spills over into how, face-to-face, he tells of his own year in hell.
"It was another whole month in the spinal unit in Sydney before I wiggled my toe. And then another toe. Each time the doctors would say, 'that's good, but maybe that's all you will do'. Frankly, they didn't know what was going to happen to me."
In the novel, Toltz - who for 10 months has been living in New York with his French girlfriend (now wife) Marie, and their three-year-old son, Marlowe - distils his own experience into the principal character, Aldo Benjamin, a sharp-talking, serial failure of an entrepreneur on whom fate never seems to smile. There are unfounded accusations of rape, beatings, a spell in prison and terrible crashes, one of which leaves him a wheelchair user.
Aldo's suffering turns his thoughts repeatedly to suicide. Is that art reflecting life? "Certainly there were dark times - for example, at 3am in a hospital, with nurses coming in to turn you every two hours. You don't get much sleep.
"I think, though, for practical purposes, positivity and denial can have the same effect. There's positivity, as in 'I am going to get though this', and then there is denial: 'This is not happening to me. I am going to get up tomorrow.' It's not positive, exactly. And I was probably in denial for a good chunk of the time."
He did, though, pull through, after four months in hospital, and many more walking with crutches and then a stick. "In all," he says, "I think it was probably nine months before I got rid of the cane, but I can't remember exactly."
Today, as he ambles along the pavement outside the hotel for the photographer to take pictures, Toltz gives no clues that here is a man who spent months learning how to walk again.
"I recovered slowly, slowly. I did a lot of rehabilitation - first standing up holding on to bars, then moving on to a walker, then crutches. When I was on the walker, I realised I would walk again, but I was having quite severe spasms in my legs, so it was not clear how I would walk. It was an ordeal. The rehab unit was shared with people who had had strokes. It was a pretty grim place."
Quicksand is, of course, a novel, not a memoir, so how much of him is there in Aldo? "Quite a lot. Certainly the only strictly autobiographical element is Aldo's time in hospital. And that I have written as a poem because I really don't like to write memoir."
In one stanza it reads: "Each night I am turned like sausages, manhandled in the murk/of sleep. Hairy hands, enhanced interrogation techniques./I wake midroll screaming/for amnesty".
"And there are parts of me," Toltz continues, "in the section after Aldo leaves hospital - about being institutionalised, about fear of leaving hospital, about people's reaction to someone in a wheelchair, and throughout the whole book about the fear of suffering and how strangely we are not changed by our life- changing events."
Many who survive life-threatening illness talk about how it leaves a lasting mark, physically and emotionally. Toltz is emphatically not one.
"Character is such a set thing. If you are optimistic and joyful and energetic before, you are the same in your wheelchair. If you are lazy and grumpy and pessimistic, you were exactly that in your wheelchair. It might exacerbate natural tendencies, but it is the stuff of fiction to be changed by life-changing events."
He counts himself more at the optimistic end of the spectrum, "because you have to be positive for someone else - at the time my girlfriend, now my child - and that ends up being good for you". But, at heart, his attitude to what happened to him from collapse to recovery is simply that it all comes down to luck.
"It irritates me beyond belief when you are told, 'have a positive attitude - you can do anything if you put your mind to it'. From my rehab, I put 92 per cent effort in because I have an in-built laziness, but I saw people who put in 100 per cent of effort. They were in the gym at 8am when it opened and stayed until it closed. I recovered, and they did not.
"I find it a great insult to them to suggest that they somehow did not have the will to do it. It was luck, and the whole experience has confirmed my belief about luck being the overriding power of the universe for us humans. It is a deeply uncomfortable thought, I know, but things just happen."