"A page-turner with the momentum of an Aaron Sorkin screenplay."—Kirkus Reviews

A New York Times 'New Nonfiction Everyone Will Be Talking About in 2026' selection

An eye-opening and wildly entertaining book about the multimillion-dollar fitness phenomenon CrossFit and its mercurial founder, Greg Glassman—from an investigative journalist and regular contributor to the New York Times.

How did an upstart workout regimen, begun out of commercial gyms in Santa Cruz in the ‘90s, become one of the most popular and polarizing fitness platforms in the world? And who, exactly, is the person responsible for its success?

The Glass Box is a page-turning and upsetting look at CrossFit—one of the most popular fitness programs in the world—and at its divisive founder, Greg Glassman. Written by veteran journalist Calum Marsh, it is both a thorough history of a company’s rise and an eagle-eyed examination of what happens when a visionary idea marches headlong toward global expansion.

CrossFit is a phenomenon, and its studios and methods are now ubiquitous. But the company’s culture of unapologetic machismo, and the sometimes reckless behavior of Glassman and his cronies, repeatedly put the brand, and its founder, in the hot seat—until one careless mistake too many brought the empire crashing down.