Big article in the most recent New Yorker on Scientology, centered around the Hollywood personality Paul Haggis. The piece, by Lawrence Wright, does not paint a rosy picture of the religion. Some of it is downright freaky–assaults, kidnappings, child slavery, all of which the church categorically denies.
Haggis, a well-known and awarding-winning writer, director, and producer, was a big cog in the machinery of L. Ron's Hubbard's religion until he had a falling out with them over Prop 8 in California, and resigned.
I have only small personal experiences with this. Back in the last sixties, when we moved to L.A., I went to a presentation on Scientology, because I thought it had something to do with science. I was unmoved by the talk, didn't hear any "science" connected to it, and went on my way. Not my thing, and if people wanted to go down that road, it was none of my business–you should be allowed to go to hell in your own way, as long as you don't drag me along.
Later, I met a science fiction writer who had gotten deeply into the stuff, and made to the stage known as "Clear." Which, according to this piece, is that a Scientology Clear is to normal people as normal people are to those who are insane. It's not the highest level, that one involves numbers–OT VIII, and that apparently gets ramped up now and then–but folks at that level are really supposed to have their shit together.
If you look at the philosophical underpinnings of religion, there are things that don't parse logically and must be accepted on faith. The old adage is, For those who believe, no explanation is necessary; for those who don't, no explanation is possible. But if you have trouble with the notion of Jesus's miracles, then what Scientology offers as as cosmology is really apt to strain credulity. Wright, quoting from an article in The Los Angeles Times in 1985, during a lawsuit in which the litigant sued the church and was awarded thirty million dollars (later reduced to 2.5 million):
“'A major cause of mankind’s problems began 75 million years ago,' the Times wrote, when the planet Earth, then called Teegeeack, was part of a confederation of ninety planets under the leadership of a despotic ruler named Xenu. 'Then, as now,' the materials state, 'the chief problem was overpopulation.' Xenu decided 'to take radical measures.' The documents explained that surplus beings were transported to volcanoes on Earth. The documents state that H-bombs far more powerful than any in existence today were dropped on these volcanoes, destroying the people but freeing their spirits—called thetans—which attached themselves to one another in clusters. Those spirits were 'trapped in a compound of frozen alcohol and glycol,' then 'implanted' with 'the seed of aberrant behavior.' The Times account concluded, 'When people die, these clusters attach to other humans and keep perpetuating themselves.'”
Anyway, my science fiction guy told me some tales about what happened to people who left the church and went public, and how very dangerous that was; tales of hit squads and dirty-tricks, and at the time, I thought that was weird, but since he was kind of flaky himself, I shrugged that off.
A bit of history: Scientology came from Dianetics, written by Hubbard, who was science fiction and fantasy writer in the 1940's. Until he went into this, he was most known for being the first science fiction writer to buy and use an electric typewriter.
There are several variations of the story, and I have heard it from two writers who said they heard it directly from Hubbard's lips when he supposedly said something to the effect of, Guys, there's no future in writing for a penny a word magazines–if you want to make real money, you need to start a religion.
Some of the variations talk about a million bucks, but there are enough writers who offer that they were there and heard him say it that would seem to have a basis in fact.
Whatever else L. Ron Hubbard was, he was canny. And the church founded on his work quickly realized that recruiting high-visibility members, such as movie stars, would be a good thing, and managed to court and bring into the fold more than few. If you know anything about it at all, you probably know that Tom Cruise, Kirstie Alley, John Travolta, and Nicole Kidman, Jenna Elfman are/were members. (Kidman has since left the church.)
It certainly seems to be a rather large can of worms opened, and I found it fascinating, in the watching-a-slow-motion-train-wreck sense.
If you want to see some interesting allegations about various high-profile members and what they are into, further reading here.