I read Amanda Montell's Cultish: The Language of Fanaticism more or less on a whim, and found myself reading it really pretty fast. It helps that she picked some high profile cults to discuss: like it or not, there's a certain fascination surrounding events like the suicides of Jonestown and Heaven's Gate. Most people have also come across the lesser examples she discusses, like fitness groups that seem to have their own language.

All in all, it's a bit of a history of prominent cults and an examination of similar principles in other arenas -- analysing what makes leaders of cults compelling, and how the same tactics work in more prosaic contexts. In and amongst all this, Montell discusses her own brushes with cults: the one her father's family were involved in, and her own experience of an attempted recruitment to Scientology.

I think a lot of this could have been said in a significantly short book, but she did identify some interesting commonalities and ways of speaking, theories about "cultish" speech that do seem to hang together.