Author Mark Haddon was known as a successful children's author, with 16 titles under his belt, before publishing his first book for adults.
But far from distancing himself from the children's market his book, The Curious Incident of the Dog in Night-Time, was embraced by both children and adults.
Haddon has written 16 children's books
Now the book has won the £25,000 Whitbread book prize.
Stroke of luck
Unusually, the book has now won awards in both adult and children's categories.
Haddon says that during the writing process he saw The Curious Incident as a book for adults, but it was his agent who recognised the appeal it would have to children because the central character was a teenager.
"Like most writers, I wrote for myself and as 41-year-old I saw it as an adult book," said Haddon.
The fact there was a wider appeal was a "happy stroke of luck".
But Haddon is wary of the "crossover" label attached to books read by both adults and children.
"I think there is a lot of hype about crossover books but this is perpetuated by marketing people and journalists.
"Young people have always read books that were aimed at adults and vice versa, it is certainly not new but it is a great thing."
Haddon's critically-acclaimed novel is written through the eyes of 15-year-old Christopher Boone who has Asperger's Syndrome, a form of autism.
The sensitive subject of Asperger's Syndrome sounds like an unlikely topic for a funny and moving book, and the author admits he did little research before embarking on the book.
Two book covers were produced. One for adults...
But he had previously worked with a number of children with varying disabilities so had what he described as a lay persons knowledge of the condition.
He did not want the condition to be all the character was about, saying "the trick is to make them seem like a human being" because you cannot lump together diverse traits of group of people into one character.
Haddon said he had received a lot of positive feedback from people affected by Asperger's, for which he said he had been "touched and moved".
There have been a few negative ones as well, but far less than Haddon had expected.
"It is a very sensitive area and its an area people feel they own if they are affected by it. People can understandably feel sensitive if other others write about it.
"People will say 'that's not like me' if they have Asperger's, or 'it's not like the ones I know with it', but that is missing the whole point that everyone is different."
Despite the success of The Curious Incident of the Dog in the Night-Time, and readers' love of the 15-year-old character, Haddon is adamant he will not be writing another book about the teenager. No doubt to the chagrin of his publishers.
"It would be like a second helping of chocolate, it would just make you feel sick," joked Haddon.
The story of the often insular world of Christopher Boone has now been optioned as a movie, which Haddon says he finds bizarre every time he talks about it, with Brad Pitt's production company set to co-produce.
...and one for children
Haddon has TV scriptwriting experience, having written Fungus the Bogeyman, but he will not be involved in the movie other than in an "informal" role, believing it is right to hand over the reins.
The complex nature of the lead character makes it difficult to imagine how the book will translate on to the big screen, but Haddon has every confidence in the ability of screenwriter Steven Kloves.
Kloves received an Academy Award nomination for the Wonder Boys and has also written the screenplays for the Harry Potter movies.
Haddon has now begun work on another novel for adults, which has the working title Blood and Scissors.
He has around five early unpublished manuscripts for adult books lying around but Haddon said he had recently come to the liberating conclusion that they were in fact "rubbish".