Penguin Books' extensive and affordable non-fiction list brought psychological ideas to a mass-market British readership. Even modestly successful titles sold thousands of copies per annum, while best sellers could sell hundreds of thousands over their lifetime. Covering a period from the mid-1940s to around 1980, Penguins on the Couch shows how psychological ideas were filtered and shaped by the inner life of Penguin Books as a commercial publisher with a commitment to professionalism, public education, and progressive politics. Penguin supplied and built a market for psychological knowledge in an era when these ideas were increasingly important – in clinical settings, in childcare and education, in progressive politics, and in the need to make sense of one's life as an autonomous individual.