The curious incident of the debut novel that sold a million in a year

J K Rowling has a rival in the super-seller stakes, and aspiring authors take note: to be The Next Big Thing in publishing, you have to be original.

No one had thought of a young student-wizard living in modern Britain before Rowling dreamed up Harry Potter. And no one had thought of a semi-autistic teenage fan of Sherlock Holmes solving a mystery before Mark Haddon created Christopher Boone, the 15-year-old narrator-hero of The Curious Incident Of The Dog In The Night-Time.

Haddon's book has turned out to be a gigantic success. Yesterday his delighted publishers, Random House, announced that his much-lauded novel, aimed at both adults and children, had now sold more than a million copies around the world, and was going out of the bookshops at a pace matched only by Rowling's Hogwarts saga.

"The demand from readers of all backgrounds and all ages has been extraordinary," said Random House's Mike Broderick. "With the exception of Harry Potter, we believe that this is the first time a book has sold one million copies in the adult and children's market so soon after publication."

The Curious Incident was published in June last year with but a fraction of the razzmatazz surrounding Harry Potter And The Order of the Phoenix, the fifth of the schoolboy-wizard's adventures.

But it has slowly built up an enormous following, aided by the cluster of literary prizes it has garnered along the way (17 around the world at the last count, with the Whitbread Book of The Year at the top of the list), and a substantial word-of-mouth effect. It's the book everybody's reading this summer: on crowded buses and trains it is possible to see three copies being read within feet of each other.

But Haddon has not taken the literary world by storm with his very first effort, as did Rowling. He was already an established children's author (and an illustrator to boot) with 15 books to his credit, going back to Gilbert's Gobstopper published in 1987.

The Curious Incident was his first book aimed specifically at adults, but not the least of its attractions (and doubtless one of the reasons for its commercial success) is that it is aimed at children too. And in a very imaginative marketing ploy, it was published simultaneously in both adult and children's imprints. (It is available for young adult readers from David Fickling Books and for adults from Jonathan Cape). It has now sold co-editions in no fewer than 15 other countries.

Originality marks it from the start. Christopher Boone lives in Swindon and has Asperger's syndrome, a mild form of autism: he is brilliant at maths but not good at people. His discovery of the neighbour's dog dead on the lawn, and his attempt to find out who killed it, lead him on a journey of discovery which ends up with the surprising truth about himself.

Although a professional author for most of his life (he is now 41), Haddon does have experience of physical and mental handicap, which he gained when he worked for Community Service Volunteers in Scotland after leaving Oxford with an English degree.

He now lives in Oxford with his wife, Sarah, (a lecturer in English and Fellow of Brasenose College), Alfie, three, and Zack, seven months, and last night he reflected wryly on his booming bestseller.

"It's certainly very flattering to think that the book's selling anywhere near the amount of J K Rowling's, as she's certainly the benchmark for book sales," he said. "Early on I was completely flabbergasted by the book's success and I continue to be totally amazed to this day.

"I keep on thinking I'm going to wake up in a hospital bed with a doctor telling me that I've had a blow to the head and it's still 2002. When I told people I was writing a book about a disabled boy living in Swindon, you can imagine the reaction."

The success has not changed him, he says, except that he now spends up to an hour each morning responding to letters and e-mails. And he wonders whether it would be "nice" to retire to a monastery in the Outer Hebrides.

Asked what he would be doing with the proceeds, he said: "I really haven't thought. But that's one of the nicer problems to have, isn't it? It's at times like this that you find out what sort of a person you are and I now know that I'm clearly not the type to go out and buy a Ferrari. Maybe I'll go and get that ticket to the monastery in the Outer Hebrides."

And the Next Big Thing from Mark Haddon? "My next project is a book with the working title of Blood and Scissors and all I can say at the moment is that it will be a comedy about nervous breakdown and skin cancer."

TOP-SELLERS

J K Rowling's Harry Potter and the Order of the Phoenix is the fastest-selling book ever, according to several chains. Tesco was selling 220 copies a minute in the first 24 hours of its release in June 2003. The book, the fifth in the series, is popular with children and adults.

The Da Vinci Code, by Dan Brown, is the biggest book phenomenon since Harry Potter. In the story, an international murder mystery turns into a quest to uncover some of Western civilisation's greatest secrets. Published last year, it sold six million copies in its first year.

Living History, Hillary Clinton's memoirs of life with the former US president sold 200,000 on its first day in the US last year, and a million in its first 12 months. Sales of Bill Clinton's memoir, My Life, published last month, have crossed the one million mark.