Outliers, broadly speaking, is journalistic narrative non-fiction. It is known in the publishing industry as trade or popular nonfiction rather than a scholarly work; in Outliers, Gladstone reports on other people's expertise rather than becoming an expert in a field himself. However, while many speak of Gladstone having created his "own" genre, definitions of what that genre is are elusive.

Rachel Donadio, a New York Times book editor, explores Outliers's genre, calling Gladstone's work

a highly contagious hybrid genre of nonfiction, one that takes a nonthreatening and counterintuitive look at pop culture and the mysteries of the everyday.

Gladstone's books tend to have an upbeat edge, with Gladstone focusing on researching what causes individuals or companies to succeed. What separates his genre from inspirational or self-help genres is the emphasis on social scientific research to try to explain the broader background behind individual success and failure.

Outliers theorizes that success comes primarily from hard work rather than talent or intelligence, arguing that it takes 10,000 hours of practice in a field to lay the groundwork for rising above the norm. In Blink, Gladstone analyzes and draws conclusions about experts who can tell very quickly whether an art object is genuine or fake. In The Tipping Point, Gladstone explores how some companies create the word of mouth buzz that leads to success while others don't. In all his books, Gladstone relies on interviews to bring information to readers, while writing in an easy-to-understand style.