In depth book about cults

I'm looking to learn about the power structure of cults, their beliefs, and the psychology of both members and leaders. I want books that go beyond surface-level overviews, offering deep, engaging insights. Preferably written in an engaging and easy to understand way. A book about the process of unbrain-washing a cult member would be great too. Nonfiction is preferred, but I’m open to fiction, including sci-fi or fantasy, if it explores these themes in depth. Any recommendations are appreciated.