The anticipated incident: Hot favourite wins Whitbread award

Mark Haddon, the novelist whose ability to enter the mind of a teenager suffering from a form of autism produced a much-loved bestseller, has won the Whitbread Book of the Year Award.

The 40-year-old writer's book The Curious Incident of the Dog in the Night-time took the £25,000 overall prize last night after its earlier triumph in the Whitbread category award for novels. Joan Bakewell, the broadcaster, who chaired the final judging panel, praised Haddon's "absolutely fantastic'' achievement in giving a voice to his 15-year-old hero with Asperger's syndrome.

Haddon's novel was published simultaneously in children's and adult editions. It is already a multiple award-winner, which has sold more than 150,000 copies, with rights deals in 40 countries.

Professor John Carey praised it as "masterly'' last autumn and lamented his failure to persuade his fellow judges of the Man Booker Prize to shortlist it. The Curious Incident picked up a South Bank Show award for literature at the weekend. It was the hottest favourite for many years in the Whitbread race, with closing odds of 11-8 on and 45 per cent of the popular vote on the Whitbread website.

Yet The Curious Incident proved far from a dead cert. Haddon narrowly came out ahead of Don Paterson, the Scottish poet. His third collection, Landing Light , has received more rapturous praise than any other British book of verse in many years.

Bakewell described the judges' deliberations yesterday as "a long and complicated debate''. Fellow judges included Andrew Motion, the Poet Laureate, as well as the actress Meera Syal, the actor Ralph Fiennes, and the writers Bill Bryson and Tim Lott.

Haddon lives in Oxford and has published 14 books for children as both writer and illustrator. After graduating in English at Oxford University, he worked with several disability charities in Scotland and in London, before becoming a full-time author.

The Curious Incident reveals his remarkable talent for empathising with a narrator whose world makes perfect sense to him but to none of the adults who surround him. The novel's hero, Christopher Boone, lives in a mental landscape of logical certainties and mathematical puzzles. He is a stranger to the turbulent emotions that obsess his single father and his schoolmates. The book not only portrays Christopher's bizarre and entrancing imagination, but allows readers to discover the family trauma and tragedy that lurks just beyond the edge of his vision.

Haddon told The Independent last week that his protagonist "turns out to be a really good narrator because he leaves a lot of space for you to add your own stuff to the story''. Hundreds of thousands of enthusiastic readers already agree with him; last night, the Whitbread judges added their voice. Bakewell said that it was extraordinary how Haddon had managed to work within the limitations set by using the voice of a boy with that sort of disability. She said: "He manages, without patronising the boy's voice, to reveal the child as a tender and thoughtful person and we see, through the boy, the chaos of the adult world around him."

But she said, although Haddon emerged as the winner, the judges wanted a special mention for the poetry of Paterson.

She said: "It was something special, an outstanding piece of poetry. We felt there was something important in the world of poetry here.''

Beside Haddon and Paterson, three other writers were shortlisted for the Whitbread award.

Each has already won a £5,000 category award. They were D B C Pierre, for his first novel Vernon God Little , D J Taylor, for his biography of George Orwell, and David Almond, for his children's book The Fire-Eaters .

A CURIOUS INCIDENT...

It was seven minutes after midnight. The dog was lying in the middle of the lawn in front of Mrs Shears' house. It looked as if it was running on its side, the way dogs run when they think they are chasing a cat in a dream. But the dog was not running or asleep. The dog was dead. There was a garden fork sticking out of the dog. I decided that the dog was probably killed with the fork because I could not see any other wounds and I do not think you would stick a garden fork into a dog after it had died for some other reason.

I went through Mrs Shears' gate and knelt beside the dog. I put my hand on the muzzle of the dog. It was still warm.

The dog was called Wellington.I stroked Wellington and wondered who had killed him, and why.

From the opening of The Curious Incident of the Dog in the Night-Time by Mark Haddon