"The Adversary" is a true crime book written by Emmanuel Carrère that explores the life of Jean-Claude Romand, a man who lived a double life for nearly two decades. Romand pretended to be a successful doctor while actually failing to complete his medical studies. His deception led to a tragic outcome when he murdered his family to cover up his lies. The book delves into themes of identity, deception, and the psychological factors that drive individuals to commit heinous acts. Carrère's narrative combines investigative journalism with psychological insight, providing a chilling look at the complexities of human behavior and the consequences of living a lie.