American Psycho, Bret Easton Ellis.

American Psycho is a chilling portrait of 1980s Manhattan, where wealth, power, and moral decay intertwine. At the centre is Patrick Bateman, a successful investment banker by day and a psychopathic killer by night. Beneath his polished exterior lies a disturbing, hollow existence, consumed by consumerism, superficiality, and violence. As Bateman spirals deeper into madness, Bret Easton Ellis masterfully blurs the line between reality and delusion, creating a biting satire of yuppie culture. Both a disturbing psychological thriller and a scathing social critique, American Psycho exposes the darker impulses lurking beneath the surface of modern life. (from: Pan Macmillon's "Must Reads: 50 best books of all time")