Book excerpt: What if society wasn't fundamentally rational, but was motivated by insanity? This thought sets Jon Ronson on an utterly compelling adventure into the world of madness. Along the way, Jon meets psychopaths, those whose lives have been touched by madness and those whose job it is to diagnose it, including the influential psychologist who developed the Psychopath Test, from whom Jon learns the art of psychopath-spotting. A skill which seemingly reveals that madness could indeed be at the heart of everything . . . Combining Jon Ronson's trademark humour, charm and investigative incision, The Psychopath Test is both entertaining and honest, unearthing dangerous truths and asking serious questions about how we define normality in a world where we are increasingly judged by our maddest edges. 'The belly laughs come thick and fast – my God, he is funny . . . provocative and interesting' – Observer