''I am 15 years and 3 months and 2 days,'' says Christopher Boone when asked his age. He is very good at what he calls ''Maths''; his father has never had to write down his bankcard PIN: He simply told it to Christopher ''because he said I'd never forget it. And it was 3558.'' Christopher doesn't like to be touched, and when asked questions too quickly, they ''stack up in my head like loaves in the factory where Uncle Terry works.'' He is then moved to lie down on the ground and make ''the noise Father calls groaning.''
Christopher is, you see, a British boy with autism, and in Mark Haddon's entrancing debut novel, The Curious Incident of the Dog in the Night-Time, the lad narrates a short period in his life with brisk logic and rollicking or heartbreaking humor that in either case reflects the solemn literal-mindedness of his condition (when a train-ticket seller asks him how long he plans to stay in London, he replies, ''Until I go to University''). Christopher solves a mystery or two, just like a favorite fictional hero of his, Sherlock Holmes. While the only initial crime to be solved is learning who killed a neighborhood dog named Wellington, the novel eventually encompasses Christopher's quest to determine whether or not his mother is dead, which his father has told him but the teenager cannot quite believe.
Haddon, a veteran children's-book author who used to work with autistic individuals at an adult training center, never goes for cheap poignancy or facile irony. He makes clear what a trial Christopher can be when, for example, he occasionally throws tantrums in public or vomits from overstimulation -- but also how pleasurable it must be, on some level, to interpret the world from such an innocent, nonjudgmental point of view. Besides, Christopher also has an awfully nice way with a simile, as when he describes a policeman's hairy nose as looking as though ''there were two very small mice hiding in his nostrils.''
Haddon's technical masterstroke is in having Christopher narrate the story so that the reader must infer the true characters of the boy's long-suffering father; his school counselor, Siobhan; and his elderly neighbor, Mrs. Alexander, who helps Christopher in his mystery-solving once they get over an awkward initial period of learning how to converse with each other. (''I can't do chatting,'' Christopher says simply, and how many among us haven't wanted to say that to someone?) If The Curious Incident, through its careful accretion of Christopher's details, eventually becomes, as he puts it, ''a mystery that isn't a mystery,'' it is also a novel that isn't just a novel. Haddon's book illuminates the way one mind works so precisely, so humanely, that it reads like both an acutely observed case study and an artful exploration of a different ''mystery'': the thoughts and feelings we share even with those very different from us.