From The Guardian:
Lafayette Ronald Hubbard published Dianetics: The Modern Science of Mental Health in 1950. According to Bridge Publications, itself an arm of the Church of Scientology, at least 80 million copies have been sold. That sounds possible, if you credit the church's claim that it has 8 million members. But then you have to reckon with more objective external estimates that the membership might be just 50,000, while one assumes that the book sales are inflated by deliberate bulk-buying by church members. So what are you going to believe?
…All of which would begin to bear out the thought that there can't be that many people who would fall for the preposterous doctrine of Scientology, or be ready to tolerate the ugly behaviour of its church. Admittedly, that is a personal opinion, but on your behalf I have acquired it from reading Lawrence Wright's account of this phenomenon. His book is admirably judicious and thoroughly researched (within the limits of secrecy or paranoia imposed by the church), but I often had the feeling that Wright himself was uncertain whether this was fit material for a sober book of non-fiction, or would he collapse in fits of helpless laughter and tears at the stuff he was obliged to report? Even if the church had just three remaining members (Tom Cruise, John Travolta and its present leader, David Miscavige), it would be a demented venture worthy of Mel Brooks or Monty Python. When I say on your behalf, I have to tell you, and remind myself, that fears of litigation are preventing publication of this book in Britain. Both the Church of Scientology and Tom Cruise have a history of being litigiously aggressive, and both have denied the veracity of a great deal of the material in the book.