What suggests in this book that Christopher may have autism? In Mark Haddon's 'The Curious Incident of the Dog in the Night-time.'
Although the word 'autism' never appears in the text, Christopher talks about his problems and the fact that he is seeing a therapist. His fixation on numbers and his inability to screen out unnecessary information are only two symptoms of Asperger Syndrome (a 'mild' form of autism). Christopher has a hard time deciphering body language and expressing himself as well. For example, when his mother cries he notices "tears coming out of her eyes" but does not make the connection that this is because she is sad. When under a sensorial "overload," he becomes panicky and goes easily into a temper tantrum, much as a very young child.
On the other hand, Christopher has a photographic memory and is a mathematical "whiz kid" (also typical of Asperger "carriers"). He is capable of reflection (even if the wrong deductions in logic are made) and of being ambitious in terms of his future. He is already studying higher mathematics and is anxious about passing his exams, even if he is supposedly too young to even be considered a candidate!
Everything about Christopher is unique and different. If he is not a particularly endearing character, the reader nevertheless picks up on the protagonist's feelings of frustration and alienation as an "outsider" balancing somewhere on the fragile rim of normalcy.