Outliers has two parts: "Part One: Opportunity" contains five chapters, and "Part Two: Legacy" has four. The book also contains an Introduction and Epilogue. Focusing on outliers, defined by Gladwell as people who do not fit into our normal understanding of achievement, Outliers deals with exceptional people, especially those who are smart, rich, and successful, and those who operate at the extreme outer edge of what is statistically plausible. The book offers examples that include the musical ensemble The Beatles, Microsoft's co-founder Bill Gates, and the theoretical physicist J. Robert Oppenheimer. In the introduction, Gladwell lays out the purpose of Outliers: "It's not enough to ask what successful people are like. [...] It is only by asking where they are from that we can unravel the logic behind who succeeds and who doesn't." Throughout the publication, he discusses how family, culture, and friendship each play a role in an individual's success, and he constantly asks whether successful people deserve the praise that we give them.
The book begins with the observation that a disproportionate number of elite Canadian hockey players are born in the first few months of the calendar year. The reason is that since youth hockey leagues determine eligibility by calendar year, children born on January 1 play in the same league as those born on December 31 in the same year. Because children born earlier in the year are bigger and more mature than their younger competitors, and they are often identified as better athletes, this leads to extra coaching and a higher likelihood of being selected for elite hockey leagues. This phenomenon in which "the rich get richer and the poor get poorer" is dubbed "accumulative advantage" by Gladwell, while sociologist Robert K. Merton calls it "the Matthew Effect", named after a biblical verse in the Gospel of Matthew: "For unto everyone that hath shall be given, and he shall have abundance. But from him that hath not shall be taken away even that which he hath." Outliers asserts that success depends on the idiosyncrasies of the selection process used to identify talent just as much as it does on the athletes' natural abilities.
A common theme that appears throughout Outliers is the "10,000-Hour Rule", based on a study by Anders Ericsson. Gladwell claims that greatness requires enormous time, using the source of The Beatles' musical talents and Gates' computer savvy as examples. The Beatles performed live in Hamburg, Germany over 1,200 times from 1960 to 1964, amassing more than 10,000 hours of playing time, therefore meeting the 10,000-Hour Rule. Gladwell asserts that all of the time The Beatles spent performing shaped their talent, and quotes Beatles' biographer Philip Norman as saying, "So by the time they returned to England from Hamburg, Germany, 'they sounded like no one else. It was the making of them.'" Gates met the 10,000-Hour Rule when he gained access to a high school computer in 1968 at the age of 13, and spent 10,000 hours programming on it.
In Outliers, Gladwell interviews Gates, who says that unique access to a computer at a time when they were not commonplace helped him succeed. Without that access, Gladwell states that Gates would still be "a highly intelligent, driven, charming person and a successful professional", but that he might not be worth US$50 billion. Gladwell explains that reaching the 10,000-Hour Rule, which he considers the key to success in any field, is simply a matter of practicing a specific task that can be accomplished with 20 hours of work a week for 10 years. He also notes that he himself took exactly 10 years to meet the 10,000-Hour Rule, during his brief tenure at The American Spectator and his more recent job at The Washington Post.
Reemphasizing his theme, Gladwell continuously reminds the reader that genius is not the only or even the most important thing when determining a person's success. Using an anecdote to illustrate his claim, he discusses the story of Christopher Langan, a man who ended up owning a horse farm in rural Missouri despite having an IQ of 195 (Gladwell claims that Einstein's was 150). Gladwell points out that Langan has not reached a high level of success because of the dysfunctional environment in which he grew up. With no one in Langan's life and nothing in his background to help him take advantage of his exceptional gifts, he had to find success by himself. "No one—not rock stars, not professional athletes, not software billionaires, and not even geniuses—ever makes it alone", writes Gladwell.
Later, Gladwell compares Langan with Oppenheimer, the father of the atomic bomb. Noting that they typify innate natural abilities that should have helped them both succeed in life, Gladwell argues that Oppenheimer's upbringing made a pivotal difference in his life. Oppenheimer grew up in one of the wealthiest neighborhoods in Manhattan, was the son of a successful businessman and a painter, attended the Ethical Culture Fieldston School on Central Park West, and was afforded a childhood of concerted cultivation. Outliers argues that these opportunities gave Oppenheimer the chance to develop the practical intelligence necessary for success. Gladwell then provides an anecdote: When Oppenheimer was a student at University of Cambridge he attempted to poison one of his tutors. He avoided punishment, and continued his studies by using the skills gained from his cultivated upbringing in his negotiation with the university's administrators, who had wanted to expel him.
In chapter nine, Marita's Bargain, Gladwell advances the notion that the success of students of different cultures or different socio-economic backgrounds is in fact highly correlated to the time students spent in school or in educationally rich environments. He describes the Knowledge is Power Program (KIPP) which helps students from about 50 inner city schools across the United States achieve much better results than other inner city schools' students and explains that their success stems from the fact that they simply spent more hours at school during the school year and the summer. Gladwell also analyzes a 5-year study done by Karl Alexander of Johns Hopkins University, demonstrating that summer holidays have a detrimental effect on students of disadvantaged backgrounds, who paradoxically progress more during the school year than students from the highest socio-economic group.
Before the book concludes, Gladwell writes about the unique roots of his Jamaican mother, Joyce, a descendant of African slaves. Joyce attended University College in London, where she met and fell in love with Graham Gladwell, a young mathematician. After moving together to Canada, Graham became a math professor and Joyce a writer and therapist. While Gladwell acknowledges his mother's ambition and intelligence, he also points out opportunities offered to his parents that helped them live a life better than those of other slave descendants in the West Indies. Gladwell also explains that, in the 18th century, a white plantation owner in Jamaica bought a female slave and made her his mistress. This act inadvertently saved the slave and her offspring from a life of brutal servitude. As one of the slave's descendants, this turn of luck led to Gladwell's relatively successful position in life. Summarizing the publication, Gladwell notes that success "is not exceptional or mysterious. It is grounded in a web of advantages and inheritances, some deserved, some not, some earned, some just plain lucky", and at the end of the book, he remarks, "Outliers wasn't intended as autobiography. But you could read it as an extended apology for my success."