The book was joint winner of the 2004 Boeke Prize, won the 2003 Whitbread Book of the Year award and sold more than two million copies. Haddon also was one of the winners of the 2004 Alex Awards, which "honor the 10 top adult books with appeal for adolescents."
As well as winning the Guardian Children's Fiction Prize, Haddon earned the Book Trust teenage fiction award. The Curious Incident of the Dog in the Night-Time was also long-listed for the Man Booker Prize, and "many observers were surprised that it did not advance to the shortlist." John Carey, chairman of the Booker panel of judges, told The Guardian, "We have several clashes of opinion among the judges but I found Haddon's book about a boy with Asperger's syndrome breathtaking."
A survey in Great Britain, conducted by the BBC's literacy campaign for World Book Day, found Curious Incident to be among "the top five happy endings, as voted on by readers" in novels (the others were Pride and Prejudice, To Kill a Mockingbird, Jane Eyre and Rebecca, the last of which Curious outranked).
School Library Journal praised it as a "rich and poignant novel." The San Jose Mercury News said, "Haddon does something audacious here, and he does it superbly. He shows us the way consciousness orders the world, even when the world doesn't want to be ordered," adding that "the great achievement of this novel is that it transcends its obvious cleverness. It's more than an exercise in narrative ingenuity. Filled with humor and pain, it verges on profundity in its examination of those things—customs, habits, language, symbols, daily routines, etc.—that simultaneously unite and separate human beings." A reviewer for The Christian Century described it as "an absorbing, plausible book": "The reader becomes absorbed not only in the mystery of a murdered dog and a missing mom, but also in the mysterious world of an autistic child."
A reviewer for The Atlanta Journal-Constitution wrote that the story is "a touching evolution, one that Haddon scripts with tenderness and care... a unique window into the mind of a boy who thinks a little differently, but like many kids his age, doesn't quite know how to feel." Professor Roger Soder called it "visceral" and a "delightful story," declaring, "All of us in our Spokane Book Club are special education professionals and so have considerable experience with kids with this disability, and we found the story believable."
Medical professionals' reviews
Dr. Alex McClimens, whom Muller quoted above, also wrote, "This magnificent essay in communication is compulsory reading for anyone with the slightest interest in autistic spectrum disorders. This book is also required reading for those who simply enjoy a fascinating story... we are offered a first person narrative to match anything by contemporary writers. Mark Haddon has created a true literary character and his handling of the teenage Asperger's heroic adventure is brilliantly crafted. He uses the literal mind-set of his hero to mask the true direction of the plot." Reviewer Paul Moorehead calls the book "a fairly ripping adventure story" and writes, "It's also quite a feat of writing. The actual use of language is somewhat austere—an unavoidable consequence of having a boy with autism as a narrator—but it has its own beauty, and it works. So persuasive and so effective is the construction of Christopher, not only is he a character you're rooting for, he's also the character in the story you understand the best. It's startling how believably and comfortably this story puts you into what you might have thought were likely to be some pretty alien shoes."
Reviewer David Ellis, naming Curious Incident an "ambitious and innovative novel," wrote that Haddon "manages to avoid the opposing pitfalls of either offending people with autism and their families or turning Christopher into an object of pity. Instead of becoming the focus of the plot, the autism enhances it. The unemotional descriptions amplify many moments of observational comedy, and misfortunes are made extremely poignantly." He concludes that Christopher's story is "far more enjoyable and likely to stay with you for far longer than any medical textbook."
Texas community reactions
The novel was selected as a recommended book for the 2006 Galveston Reads program, a literacy encouragement program in Galveston County, Texas. Kimball Brizendine, the Mayor of Friendswood, issued a proclamation declaring "Galveston County Reads Day" and encouraging "all citizens, teens to seniors" to read the novel. Five days later, he retracted the statement, declaring that it was "not [his] intention to endorse this readership [sic] for our younger readers." The journal American Libraries reported, "City Council member Chris Peden went a step further, asserting to the January 28 Galveston County Daily News that while he hadn't read Curious Incident in its entirety, he had noted that the 'F word' appeared on page four and that 'later in the book, the [lead character] says there is no God and there is no life after death. Clearly, these are not ideas we should promote to kids'."
In August, 2007, some parents in Bryan, Texas, "were appalled to see what their kids were reading" and protested the inclusion of the book in high school libraries, with one parent claiming that Curious Incident and another book (Catalyst by Laurie Halse Anderson) were "unsuitable for not just some but all high school students."