First person tale of Christopher, a fifteen-year-old with Asperger's Syndrome or high-functioning autism and a talent for maths, who writes a book (this one - sort of - very post modern) about his investigations of the murder of a neighbour's dog. He loves Sherlock Holmes and is amazingly observant of tiny details, but his lack of insight into other people's emotional lives hampers his investigation. Nevertheless, he has to overcome some of his deepest habits and fears, and he also uncovers some unexpected secrets.
It is primarily a YA book, but there is more than enough to it to make it a worthwhile adult read as well. It is also quite funny at times, usually arising from Christopher's naive misunderstandings of situations and the conflict between his lack of embarrassment and desire to be unnoticed by unfamiliar people.
The structure of the book (chapter numbers are all primes; inclusion of maths puzzles and diagrams) and narrative style (attention to detail, excessive logic, avoidance of metaphor) reflect Christopher's mindset and way of viewing life. It is peppered with snippets of maths and explanations of his condition: how it affects him, and what coping strategies he adopts. The effect is plausibly stilted and occasionally breathless, which is reminiscent of people I know who are on the autistic spectrum and tallies with my limited reading about the condition. (Note that neither autism nor Asperger's is mentioned by name in the book, although in my first edition, neurologist Oliver Sacks does mention it in a quote on the front cover.)
Christopher's condition makes him very literal - something he is aware of. He can analyse a joke, but still not "get" it. Truth is paramount, so he hates situations where he can't tell the truth (e.g. for politeness) and indeed the fact that "everything you tell is a white lie" because you can never give a fully comprehensive answer to anything. He also hates metaphors (even "the word metaphor is a metaphor", meaning "carrying something from one place to another"), but he doesn't mind similes because they are not untrue. Christopher's feelings about metaphors are highly pertinent to a very different book, China Mieville's wonderful "Embassytown" (http://www.goodreads.com/review/show/396183492), which is about how minds shape language and how language shapes minds, and focuses on the relationship between similes, truth and lies.
Many novels are about uncovering what is true, but Christopher's quest takes the idea to a deeper level, and even though we know this narrator is almost pathologically truthful, his condition means his observations sometimes miss the real truth of a situation.
Christopher loves maths because it is safe, straightforward and has a definite answer, unlike life. He's also good at explaining some aspects, ending an explanation of calculating primes with "Prime numbers are what is left when you have taken all the patterns away".
His apparent deviations from logic are justified with ingenious logic. For example, having favourite and hated colours reduces choice and thus stress, counteracting the effect of his inability to filter or prioritise: he notices (and remembers) every detail of everything, and can rewind it at will, whereas other people's brains are filled with imaginary stuff. He is a little like his hero Sherlock Holmes, who is quoted saying "The world is full of obvious things which nobody by any chance observes". Similarly, defining a good or bad day on the basis of how many red or yellow cars is no more illogical than an office-bound person's mood being dictated by the weather.
All of this means animals are a better bet than humans: "I like dogs. You always know what a dog is thinking - it has four moods. Happy, sad, cross and concentrating. Also, dogs are faithful and they do not tell lies because they cannot talk". People are more of a mystery: when having a conversation, people look at him to understand what he's thinking, but Christopher can't do likewise. For him "it's like being in a room with a one-way mirror in a spy film". Love is even more unfathomable: "Loving someone is helping them when they get into trouble, and looking after them, and telling them the truth, and Father [does lots of things for me]... which means that he loves me".
I reread this during a rather stressful journey, including the passages when Christopher is making a stressful journey. It helped me empathise with him - to the extent that it exacerbated my own stress!
It's worth comparing this with Iris Murdoch's The Word Child (http://www.goodreads.com/review/show/31941318), whose main character has tacit Asperger's tendencies, and The Housekeeper and the Professor (http://www.goodreads.com/review/show/339229819), which is also about finding number patterns in everyday life, and involves a protagonist whose brain does not work like other people's.