Don't Call it a Cult: The Shocking Story of Keith Raniere and the Women of NXIVM by Sarah Berman shows us the formula for creating a cult. Sleep and food deprivation; complete surrender of personal possession and money; a cohesive atmosphere swaddled in a self-help and religious ethos; long group sessions involving confessions of flaws and traumas; forced detachment from friends and family. NXIVM did all this, and it is hardly surprising that toward the end Keith Raniere created a group of women he could personally emotionally, cognitively, and sexually manipulate.
Berman’s book is scary because of what happens, but also because of how it happens. The indoctrination is gradual, and before the people in NXIVM know they are trapped it is too late. It is amazing how our social impulses can be perverted by unscrupulous, immoral people.