Published by Little, Brown and Company on November 18, 2008, Outliers debuted at number one on the bestseller lists for The New York Times in the United States and The Globe and Mail in Canada on November 28, 2008, holding the position on the former for eleven consecutive weeks. Between June 2011, when the paperback version was released, and February 2017, the book made the New York Times bestseller list for paperback nonfiction 232 times. As in his other books, Gladwell's engaging and vivid prose drew praise in Outliers, though Gladwell's methodology has been criticized for too often falling prey to fallacious reasoning, inadequate and anecdotally based sampling, and oversimplified analysis. In particular, Anders Ericsson and coauthors who conducted the study upon which "the 10,000-Hour Rule" was based have written in their book that Gladwell had overgeneralized, misinterpreted, and oversimplified their findings.
David A. Shaywitz, reviewing the book in The Wall Street Journal, praised Gladwell's writing style as "iconic", and asserted that "many new nonfiction authors seek to define themselves as the 'Malcolm Gladwell of' their chosen topic." He complimented its clarity and easy grace, but also pointed to these as possible Achilles' heels for Gladwell because of his oversimplification of complex sociological phenomena to "compact, pithy explanations". Furthermore, he praised the book for asking some important questions, such as "How much potential out there is being ignored? How much raw talent remains uncultivated and ultimately lost because we cling to outmoded ideas of what success looks like and what is required to achieve it?"
In a discussion about the book in Slate magazine, John Horgan was particularly moved by Gladwell's family history. He felt that the links between race and achievement were given substantive analysis, but found the lessons mentioned in Outliers to be "oddly anticlimactic, even dispiriting". His contribution concluded by remarking, "Outliers represents a squandered opportunity for Gladwell—himself an outlier, an enormously talented and influential writer and the descendant of an African slave—to make a major contribution to our ongoing discourse about nature, nurture, and race." BusinessWeek gave the book four out of five stars and appreciated its "Aha!" moments, but wondered if Gladwell purposely omits evidence that contradicts his thesis. The review remarked that Outliers was repetitive in parts, but that Gladwell eventually pulls the stories together into an overarching narrative.
Criticism focused on the book's style and oversimplified conceptualizations. Displeased with Gladwell's generalizations drawn from small amounts of data, Roger Gathman wrote in The Austin American-Statesman that this was uncharacteristic of him, and believed that the approach points to a "certain exhaustion in his favorite method". He remarked that in Outliers, the experiments, analyses, and conclusions drawn are too mechanically applied to historical or cultural phenomena to "create a cognitive 'gotcha' moment", that Gladwell's analytical method was no longer working, and that "it's high time for Gladwell to produce something more challenging than his beautifully executed tomb robberies of old sociology papers." Boyd Tonkin in The Independent held a similar opinion, and wondered why Gladwell "does not yet hold a tenured professorship at the University of the Bleedin' Obvious".
Jason Cowley, reviewing the book in The Guardian, felt that Outliers was an argument between Gladwell and himself, referring to the many times that he uses the word "we" when defining his position, such as in the example: "There is something profoundly wrong with the way we look at success. [...] We cling to the idea that success is a simple function of individual merit and that the world in which we grow up and the rules we choose to write as a society don't matter at all." He also believed that there was a "certain one-dimensional Americanness at work", observing that many of Gladwell's examples are from the United States, particularly in New York City. In an article about the book for The New York Times, Steven Pinker wrote, "The reasoning in 'Outliers,' which consists of cherry-picked anecdotes, post-hoc sophistry and false dichotomies, had me gnawing on my Kindle." In a review in The New Republic, Isaac Chotiner called the final chapter of Outliers "impervious to all forms of critical thinking".
Finding it ironic that Outliers provided suggestions on how to resolve cultural biases, the Sunday Times review by Kevin Jackson agreed that the book itself suffered from an unbalanced focus on American subjects, predicting that this would lead to better sales in the United States than in the United Kingdom. Jackson was disappointed in the book's lack of new ideas, noting that it merely expands on the concept that "you have to be born at the right moment; at the right place; to the right family (posh usually helps); and then you have to work really, really hard. That's about it." He was also skeptical towards Gladwell's arguments for the 10,000-Hour Rule by countering that the Beatles' success had more to do with "the youthful spirit of the age, the vogue for guitar bands and a spark of collaborative chemistry". Regarding the book, Paul McCartney, former member of the Beatles, said in an interview on August 6, 2010:
[...] I've read the book. I think there is a lot of truth in it [...] I mean there were an awful lot of bands that were out in Hamburg who put in 10,000 hours and didn't make it, so it's not a cast-iron theory. I think, however, when you look at a group who has been successful... I think you always will find that amount of work in the background. But I don't think it's a rule that if you do that amount of work, you're going to be as successful as the Beatles.
Case Western Reserve University's assistant professor of psychology Brooke N. Macnamara and colleagues have subsequently performed a comprehensive review of 9,331 research papers about practice relating to acquiring skills. They focused specifically on 88 papers that collected and recorded data about practice times. In their paper, they note regarding the 10,000-hour rule that "This view is a frequent topic of popular-science writing" but "we conducted a meta-analysis covering all major domains in which deliberate practice has been investigated. We found that deliberate practice explained 26% of the variance in performance for games, 21% for music, 18% for sports, 4% for education, and less than 1% for professions. We conclude that deliberate practice is important, but not as important as has been argued".
Statistical analyst Jeff Sauro looked at Gladwell's claim that between 1952 and 1958 was the best time to be born to become a software millionaire. Sauro found that, although the 1952–1958 category held the most births, "[a] software millionaire is more than twice as likely to be born outside the 1952 to 1958 window than within it." Sauro notes that Gladwell's claims are used more as a means of getting the reader to think about patterns in general, rather than a pursuit of verifiable fact.
Sociologist Shayne Lee referenced Outliers in his opinion editorial for CNN.com that commemorated Martin Luther King Jr.'s birthday. Lee discussed the strategic timing of King's ascent from a "Gladwellian" perspective, citing Outliers as the inspiration for his argument.