Unable to understand emotions normally, he finds many everyday events threatening and ordinary activities challenging. To cope he has surrounded himself with rules and rituals — red cars are a good sign, yellow cars a bad one; yellow and brown food can't be eaten; and so forth — and has his own coping mechanisms — he relaxes by crouching down and groaning, or by listening to white noise. And he does his best to understand the interactions of the people around him intellectually, helped by his photographic memory and mathematical talent — he's doing A-level mathematics even though he attends a "special needs" school.
The Curious Incident of the Dog in the Night-Time is not just a sympathetic and sensitive study of autism, however, but a lively and engaging story of a teenager facing a crisis. It is at the same time sad and funny, entertaining and informative, and serious and whimsical. Christopher's unusual perspective makes us see ordinary events and activities in a new light, while his abilities and limitations help drive the plot. And we are sometimes kept in suspense, even though we often know more than the narrator. (The novel purports to be Christopher's work, a conceit which is nicely maintained, although the language and style are far too polished to be the work of a fifteen year old.) Another unusual feature is the inclusion of short but genuine pieces of mathematics and science.
Haddon has taken an original idea and executed it superbly. It should go down well with geeky teenagers, but The Curious Incident of the Dog in the Night-Time is a "cross-over" book which will also appeal to adults. There are separate "adult" and "children's" editions in the UK, but this is unnecessary since the attraction is the same for both audiences: a well paced story with novel ideas.