Going Clear: Scientology, Hollywood, and the Prison of Belief by Lawrence Wright
My rating: 4 of 5 stars
Having read Inside Scientology, I knew about most of the history and scandals surrounding this religion. What Wright does (unlike Reitman) is present as neutral as possible an account, giving people credit where it's due while still highlighting the discrepancies between the official Church record and other's memories/experiences.
The other thing that Wright does very well is clarify why - or why not - Scientology could be considered a religion. This isn't something that is easy to tease out, with much of their literature declared to be a trade secret. Auditing is explained, but exactly what happens in the courses that people pay thousands (and they do pay thousands) for is never fully explained.