Claire Morrall: The author explores Asperger's syndrome in her latest novel

Clare Morrall: 'I'll never write a novel about somebody having an affair with their nextdoor neighbour' © Jonathan Evans

I am always drawn to the strange and the odd and the unusual – people on the outside looking in. I will never write a book about somebody having an affair with their next-door neighbour," declares Clare Morrall. As soon as the words are out she looks embarrassed, as if she has been too forthright, too rude about rivals. "I don't want to sound snooty about other people's writing," she adds hastily. "Other people can do the subject extremely well, I just know that I probably wouldn't be able to."

News that Morrall has no plans to write kitchen-sink dramas will relieve her readers. About to publish her third novel, the 55-year-old has a reputation for creating delightfully quirky characters whose social skills, never mind relationships, barely function. Her first published novel, the Booker-shortlisted Astonishing Splashes of Colour, featured the socially malfunctioning Kitty at the centre of an unconventional family. Her second, Natural Flights of the Human Mind, featured the reclusive former pilot Straker and his neighbour Imogen Doody. Neither was immediately sympathetic, but Morrall's confident prose drew the reader in, making these difficult people fascinating rather than repulsive.

The main protagonist in her new novel, The Language of Others, is another enigma. On first impressions, Jessica is a troublesome child, painfully withdrawn and, as Morrall admits, "difficult to deal with". As the story unfolds, her inability to read people, especially Andrew, the tantrum-throwing violinist whom she goes on to marry, is frustrating. Later, her passivity when faced with Andrew's abuse and her 24-year-old son Joel's adolescent reticence is infuriating. But as Morrall reveals Jessica's past and Jessica narrates her present, it becomes apparent that her inability to deal with the mess of human emotion is the result of undiagnosed Asperger's syndrome. By the time she finally comes to understand the language of other people's hearts, Morrall has made us identify with a woman who, like us all, is just muddling through.

Asperger's syndrome has been a popular subject since Mark Haddon's award-winning The Curious Incident of the Dog in the Night-time. Given her horror of clichéd themes, why did Morrall want to add to the burgeoning pile of "autism fiction"? "I actually think that it is because I read The Curious Incident," she admits. Though she thought the book well written, she was disturbed that it might further isolate anyone with a diagnosis on the mild end of the autistic spectrum. "I just worried that children who are less extreme might be labelled as being dangerous or very peculiar, when what they really want to do is fit in with everyone." She adds: "The side of Asperger's I wanted to write about was the milder form, where it is arguable how abnormal you are." She reflects for a moment, then scoffs: "What is 'normality'? I would argue that everybody has an element [of autism] in them."

Women with Asperger's have a tough time, Morrall believes, because their condition is often not diagnosed. "There are a lot of misconceptions about Aspeger's – one is that only boys get it," Morrall explains. Even her writing group refused to believe a woman could have the syndrome. "Because girls with Asperger's are no trouble, people don't worry about them," she says. But, as Jessica shows, without the diagnosis, life can seem lonely and inexplicable.

As Morrall talks I am reminded that, although she has two acclaimed novels under her belt, she also still teaches music to five- to 11-year-old boys at a West Midlands prep school. There is something so school-teachery about her. Not bossy or imposing; Morrall is not that kind of teacher. She is the sort to share a joke in the staff room (she laughs a lot, a dirty giggle as if she's just been told a naughty joke); the sort to enthuse pupils otherwise bored rigid, and draw out secrets buried far from the reach of playground tyrants. I had a teacher like that: Miss Forest. I haven't thought of her in years, but she had the same knowing laugh. It is hard to imagine that, without teaching, Morrall's observations of childhood malice would have been so acute.

Asperger's makes Jessica vulnerable to bullies, especially her charming, sadistic cousin Philip, who, when confronted later in life, is incredulous that he could have been so cruel. "People don't remember the nasty side of themselves," Morrall says. Jessica, like a lot of victims, buries her suffering deep within and tries to make sense of why it is aimed at her. Morrall believes that the after-effects of childhood sadism echo throughout life. In Jessica's case it prepared her for an abusive marriage. "The bullying was conditioning her, and the nature of it was such that she was unable to deal with any of it. Another person would have been able to recognise the same characteristics [of charm and cruelty] in Andrew, and reject them."

Andrew's charm masks a vicious, egocentric loser, who has already been rejected by his peers at music college for being "showy" and a flake. Unequipped to read the signs and starved of affection, Jessica is an easy victim. As such, The Language of Others is more about how and why an abused partner remains in a relationship, than how someone with Asperger's syndrome responds to one. It is a point Morrall is keen to make. "I think that it is much harder to break out of those circumstances than people realise," she explains. "Also, there is a sense of guilt: that maybe his behaviour is her fault."

Andrew hides his true character well. Though Jessica's friends may deplore his flakiness and inability to hold down a job, they do not see the emotional wounds he inflicts or the casual threats of violence – in part because Jessica covers up for him.

Morrall has a lot of sympathy for women such as Jessica, who keep their sufferings secret. It is not complicity, she says, it is more complex than that, and we should sympathise rather than judge. "People who are in very abusive marriages defend their partner because, apart from anything else, it's an attack on them as well. It's about their judgement," she explains. "It takes courage to say, 'Oh look. I have made a terrible mistake, this man is really vile and I have been pretending for some time that he really isn't.'"

Dysfunction is not limited to marriage in The Language of Others. An ongoing theme in it is the failure of different generations to understand one another – the attempts by Jessica's mutton-in-a-mini-skirt mother to "hang out" with the young are wittily observed. Morrall clearly is not of the "you are only as old as you feel" school of thinking, perhaps as a result of having spent so much time in the company of sceptical schoolchildren. "There is a huge lack of communication between generations," she observes. "Parents' and children's relationships are rarely as successful as the parents would like to think. Parents like to think they are handling a situation with calmness and maturity, and then in 20 years' time the child will say, 'You were so unfair'." As the mother of two adult children, Morrall is speaking from experience.

It was her daughter, Heather, who she jubilantly phoned when told that her first published novel had been shortlisted for the Booker in 2002. "Margaret Atwood and I are on the shortlist," she told her, laughing. Morrall's story has given hope to many unpublished ageing authors: after 20 years and three failures to get novels published, Astonishing Splashes of Colour was picked up by the tiny, Birmingham-based Tindal Street Press. She was 51, and 33 literary agents had already rejected the novel. "And Tindal Street nearly didn't take it," she recalls, laughing.

Tindal Street demanded rewrites, but she enjoys being edited and was happy to oblige. Even now that she has moved on to the swankier imprint of Sceptre, part of the august Hodder & Stoughton empire, she is more than happy to listen to her editor, Carol Welch. Not every writer who enjoys success with their first book is so pliable, and I tell her she sounds like an ideal author. "That is what I try to tell them," she says, self-mockingly. Then she adds, absently: "You need to have the eye of an outsider." It is appropriate from an author who appreciates those on the fringes and what they can teach us.

The extract

The Language of Others, By Clare Morrall Sceptre £12.99)

'...Was this a major crisis in his life, or just a blip? Did he need to be alone, or did he need me? How do you ever know these things? I thought of all the books I'd read, the films I'd seen, the conversations I'd overheard, and realised that I knew nothing. I couldn't interpret events. I didn't know how people would react, or why they said what they did. I didn't even know how my own boyfriend would be expected to behave.'