A novel written through the eyes of an autistic 15-year-old has won the Guardian Children's Fiction Prize.
Haddon's book missed out on a Booker shortlist place
Mark Haddon's The Curious Incident of the Dog in the Night-Time has been one of the surprise hits of 2003.
The book beat David Almond's The Fire Eaters to take the prize. Four books were shortlisted for the award.
"Both are simply exceptional. The Dog won the day, and in the end we were all happy with that," said judge Michael Morpugo.
Other books that made it into the shortlist were Kevin Brooks for Lucas and Alex Shearer for The Speed of the Dark.
Haddon's book - which missed out on a place on the shortlist for this year's Booker - is about an autistic teenager, Christopher Boone, who, obsessed with Sherlock Holmes, sets out to investigate the death of a neighbour's dog.
Boone is gifted at maths and puzzle-solving, but cannot read human emotions.
Haddon, who is best known as a children's author, has said he did not write The Curious Incident of the Dog in the Night-Time for kids, but saw it more of a book for adults.
But publishers took the book and released two versions, with a cover aimed at adults and one for teen readers.
Last year's prize was won by Sonya Hartnett for Thursday's Child. Other winners in the prize's 28-year-history have included Ted Hughes, Philip Pullman and Anne Fine.