Science Fiction author L. Ron Hubbard wrote a book called Dianetics: The Modern Science of Mental Health back in 1950. This made him a fair bit of money, but what he really wanted was to be tax-free. So eventually he wrapped it in a religion called "Scientology," and then the money really started rolling in. This movie is based on the book Going Clear: Scientology, Hollywood, and the Prison of Belief by Lawrence Wright, who spends some time talking on camera. He claims he didn't write the book as an exposé, but just to try to figure out what made devotees of the religion so dedicated.
I've been a fan of science fiction for many years so I knew about L. Ron Hubbard. His move to form a religion was well known and much scoffed at in the SF community, so I thought I knew something about Scientology. And most of what I knew wasn't incorrect, but there's a LOT more to know. I was fascinated to hear that the Church of Scientology blackmailed the IRS into giving them tax-exempt status: they asked all their members to sue the IRS, then after 2400 of them did, they told the IRS it would all go away if Scientology became tax-exempt. There are pictures of the Scientology brass celebrating with the IRS brass.
The most interesting stories come from those who have left the church. The most articulate and intelligent of these is Paul Haggis, a well known TV producer who left after 20 or 30 years when he found out that two of his daughters were being subjected to "cures" for their homosexuality. Others tell of the blackmail and harassment that pursues anyone who leaves the church - particularly those who speak out against it.
Well constructed, fascinating, and kind of horrifying.