I recently finished Going Clear, the Scientology exposé by Lawrence Wright. I highly recommend it.
A couple of highlights from the book:
The L. Ron Hubbard era: Hubbard, a serial bigamist and lifelong philanderer, counsels his first wife that his journey is taking him onwards, and that a divorce would reflect poorly on him. Therefore, the best thing to do would be for her to commit suicide. (She didn't.)
The David Miscavige era: Miscavige keeps several ferocious dogs around the Sea Org compound. They routinely attack members of the Sea Org. Miscavige has custom military-style outfits made for the dogs, complete with epaulets bearing their rank: Captain. Most of the human Sea Org members are outranked by the dogs, so they have to salute the dogs anytime they wander past.