In a June 2003 interview with NPR's Terry Gross on her program Fresh Air, Haddon said about Christopher, "If he were diagnosed, he would be diagnosed as having Asperger's syndrome, which is a form of autism. I suppose you'd call it high-function autism in that he can function on, you know, a day-to-day basis, in a kind of rudimentary way. But he has a serious difficulty with life in that he really doesn't empathize with other human beings. He can't read their faces. He can't put himself in their shoes. And he can't understand anything more than the literal meaning of whatever's said to him, although I'm very careful in the book not to actually use the word 'Asperger's' or 'autism.' ... Because I don't want him to be labelled, and because, as with most people who have a disability, I don't think it's necessarily the most important thing about him... And as a good friend of mine said after reading the book, a friend who is himself a mathematician, it's not a novel about a boy who has Asperger's syndrome; it's a novel about a young mathematician who has some strange behavioural problems. And I think that's right."
Haddon added, in the conversation with Terry Gross, "I have to say honestly that I did more research about the London Underground and the inside of Swindon Railway Station, where some of the novel takes place, than I did about Asperger's syndrome. I gave him kind of nine or 10 rules that he would live his life by, and then I didn't read any more about Asperger's because I think there is no typical person who has Asperger's syndrome, and they're as large and diverse a group of people as any other group in society. And the important thing is that I did a lot of imagining, that I did a lot of putting myself into his shoes in trying to make him come alive as a human being rather than getting him right, whatever that might mean."
Haddon states on his website that, although he had read "a handful of newspaper and magazine articles about, or by, people with Asperger's and autism" in preparation for writing the book, he knows "very little" about Asperger's syndrome and that Christopher Boone is inspired by two different people. According to Haddon, none of these people can be labelled as having a disability. Haddon added that he "slightly regret[s]" that the term Asperger's syndrome appeared on the cover of his novel. In 2010, in an interview with The Independent, he was described as "now thoroughly irritated that the word Asperger's appeared on subsequent editions of the novel, because now everyone imagines that he is an expert and he keeps getting phone calls asking him to appear at lectures."
In a critical essay on the novel, Vivienne Muller quotes some praise by experts on disability theory: "In its presentation of Christopher's everyday experiences of the society in which he lives, the narrative offers a rich canvas of experiences for an ethnographic study of this particular cognitive condition, and one which places a positive spin on the syndrome. The reader in this instance acts as ethnographer, invited to see what Mark Osteen claims is a 'quality in autistic lives that is valuable in and of itself' (cited in [S.] Adams 2005, p.1). Along similar lines, [Alex] McClimens writes that Haddon's novel is 'an ethnographic delight' and that 'Haddon's achievement is to have written a novel that turns on the central character's difference without making that difference a stigmatising characteristic' (2005, p.24)." Muller adds that the novel "works with a strong sense of the disabled speaking subject, drawing readers into Christopher's cognitive/corporeal space through an incremental layering of his perspectives and reactions... The narrative also bristles with diagrams, maps, drawings, stories, texts that inform Christopher's lexicon for mapping meaning in a world of bewildering signs and sounds." She also admires such elements as "the digressive stream-of-connectedness-and-disconnectedness way in which Christopher writes and thinks; the obsessive focus on minutiae; his musings about why animals behave the way they do; his quasi philosophizing on death and life and the afterlife; his ambition to be an astronaut..."
In a survey of children's books which "teach about emotional life," Laura Jana wrote, "On the one hand, this is a story of how an undeniably quirky teenage boy clings to order, deals with a family crisis, and tries to make sense of the world as he sees it. But it also provides profound insight into a disorder—autism—that leaves those who have it struggling to perceive even the most basic of human emotions. In so doing, The Curious Incident leaves its readers with a greater appreciation of their own ability to feel, express, and interpret emotions. This mainstream literary success made its way to the top of the New York Times bestseller list for fiction at the same time it was being touted by experts in Asperger's syndrome and autism-spectrum disorder as an unrivaled fictional depiction of the inner workings of an autistic teenage boy."
Christopher often comments on his inability to appreciate some metaphors and similes. He gives as an example a quote that he found in "a proper novel": "I am veined with iron, with silver and with streaks of common mud. I cannot contract into the firm fist which those clench who do not depend on stimulus." Haddon told Terry Gross, "Funnily enough, it's actually a quote from Virginia Woolf. It's Virginia Woolf on an off day, in the middle, I think, of The Waves. An author whom I love actually, but who sometimes got a little too carried away."