"I've also drawn on the lives of all the other parents I've met who are caught in the soul destroying struggle to get the right educational and medical help," says Lette.
"But while the emotion that propels the book is heartfelt and based on my own experiences, the characters, like Lucy's larger-than-life, cougar, man-stalking, adventurous mother and devoted big sister, are all conjured up from my deranged imagination. I truly believe that your women friends are your human wonderbras - uplifting, supportive and making each other look bigger and better.
Lette says the characters' devotion and support of Lucy reflects her own family's.
"I'm lucky enough to have three sensational sisters and a self-less, wise, witty and warm mother. We laugh a lot, which is nature's survival mechanism. And gin also helps."
Interviewing Lette is like reading one of her novels as she constantly peppers the conversation with sardonic one-liners and frequently embarks upon amusing anecdotes of what it is like to raise a child who suffers from "Asparagus Syndrome", as Julius likes to call it.
"Life with my deliciously quirky son has brought me much joy and hilarity," says Lette, who acknowledges that his lack of a filter often leads to comedy and chaos.
"It's like he sees life through the other end of the telescope, as he possesses a literal, lateral, tangential logic, which can be charmingly disarming. He's always asking me questions that I can't answer, like 'can you use yo-yos on the moon?'
"When you're parenting a child with Asperger's, it's best to just strap a shock absorber to your brain because they always say exactly what they're thinking, which means that you're constantly tip-toeing through a social minefield."
While its title appears to be a play on the 1976 David Bowie film The Man Who Fell To Earth, Lette's novel explores similar territory to Mark Haddon's popular best-seller, The Curious Incident Of The Dog In The Night-Time.
"The best way of describing it is The Curious Incident told from the mother's point of view," says Lette.
"People with Asperger's often say that they feel like they're drowning in their own brain waves. I just hope that in its own small way, this novel can act as a kind of literary liferaft."
More than two decades since she first moved to London, Lette maintains that she is still an outsider in Britain, something that she touches on in her novel with Lucy's Aussie lodger and love interest, Archie.
"Being Antipodean gives you great social mobility and you can get away with so much more mischief," she says. "Archie and I can flit from afternoon tea at Buckingham House to the housing estate with the single mums for a beer with ease. It's like being Vaseline-coated. My British writer friends can't do that. The English love to pigeonhole and
label. They're enslaved to the class system. Even their letters travel first and second class."
Lette is looking forward to attending the Auckland Writers and Readers Festival this month and will hopefully be awarded a better reception than was accorded her 1988 third novel, Girl's Night Out. "It was once actually banned in New Zealand, although I don't know why," she says. "But we used it as a banner line/selling point on the cover of the book everywhere else in the world, including America. 'Banned in New Zealand!' It was a badge I wore with pride."
However, her crucial breakthrough inadvertently occurred in Auckland.
"I owe you and your weather a lot," she laughs.
"It was while Billy Connolly was on tour there, 22 years ago, that he bought one of my novels and gave it to his wife, Pamela Stephenson. She invited me to their home in Windsor for dinner and we've all been firm friends ever since. If it hadn't been raining, he wouldn't have popped into a bookshop for shelter and picked me up, so to speak."
While she is in the country, Lette is planning to catch up with Connolly and her other good friends Stephen Fry and Barry Humphries, who are currently filming The Hobbit in Wellington.
"They're all having a blast," she says. "With exquisite cuisine, stunning scenery and warm and welcoming people who dry, wry humour, what's not to love? Although I do think you all exercise a tad too much. I suppose it's the 'zeal' in New Zealand. Everyone is so zealous, sprinting up mountains, abseiling down glaciers, jogging to work and canoeing to literary festivals. It's exhausting.
"The only things I run up are bills."
The Boy Who Fell To Earth (Random House $39.99) is out now.
