Atlas Shrugged.

“From 1943 until its publication in 1957, [Rand] worked on the book that many say is her masterpiece, Atlas Shrugged. This novel describes how a genius named John Galt grows weary of supporting a society of ungrateful parasites and one day simply shrugs and walks away. He becomes an inspiration to like-minded men and women, all of whom eventually follow his example, until society, in its agony, calls them back to responsibility and respect. Again [as with Rand’s novel The Fountainhead in 1943] reviews were unsympathetic, and again people bought the book” (ANB). The theme of Atlas Shrugged, as Rand described it, is "the role of man's mind in existence." The book explores a number of philosophical themes that Rand would subsequently develop into the philosophy of Objectivism. By 1984 more than five million copies of Atlas Shrugged had been sold, and in a 1991 Library of Congress survey Americans named it second only to the Bible as the book that had most influenced their lives. It is the basis for the trilogy of film adaptations subtitled Part I (2011), Part II (2012), and Part III (2014).