At last! It has taken over two years, but a British publisher has summoned up the nerve to bring out Going Clear, an astonishing exposé of the Church of Scientology by Lawrence Wright of the New Yorker.

Wright — who won the Pulitzer Prize for The Looming Tower, his investigation of 9/11 — is the journalistic equivalent of a virtuoso musician: he can race us through the most complicated narrative because he has done unimaginable amounts of homework.

Wright conducted hundreds of interviews for Going Clear, then had a team of fact-checkers crawl over the text. Even so, none of our big publishing houses would touch it. This UK edition comes from Silvertail Books, a one-man operation run by Humfrey Hunter, a former literary agent whose tiny catalogue also includes Russell Miller’s Bare-Faced Messiah: The True Story of L. Ron Hubbard and John Sweeney’s The Church of Fear: Inside the Weird World of Scientology.

Hunter is a brave man. Our libel laws are tougher than America’s and Scientology employs relentlessly aggressive lawyers. Also, the church’s attitude towards revelations about its founder is roughly that of Muslims to cartoons of Mohammed. Russell Miller’s life was made hell when he first published his biography of Hubbard in 1987: his family was spied upon and there were ludicrous attempts to frame him for two murders.

Wright’s book is even less flattering than Miller’s. Hubbard emerges as a priapic wife-beater who as a young science-fiction writer dabbled in Aleister Crowley’s satanic rituals, probably under the influence of narcotics. He died a recluse, his health wrecked by smoking and over-eating — and, we’re told, pumped full of the anti-anxiety drug Vistaril. These claims will infuriate the Church of Scientology, whose campaigns against drugs (especially psychiatric ones) are the cornerstone of its attempts to win public acceptance.

It won’t be pleased, either, by the discussion of Hubbard’s secret cosmology, founded on his discovery that 75 million years ago the intergalactic Emperor Xenu dropped his billions of enemies into volcanoes on Earth before blowing them up with hydrogen bombs.

That said, the Church knows it has lost the battle to suppress the Xenu story, which was related in a South Park episode (not shown in the UK) also featuring John Travolta and Tom Cruise trapped in a closet. It will be more annoyed, one suspects, by incidental details of Hubbard’s life and teachings — his belief that a foetus can ‘record’ its mother’s masturbation, for example, or his alleged reaction to the suicide of his gay son (‘That little shit has done it to me again!’).

You can’t libel the dead, of course, and all the dirt on L. Ron is in the British book. But there has been ‘some editing to accommodate legal concerns that are particular to the UK’. Obviously we’re not told what has been removed, but since the two editions use the same typesetting it’s not hard to work out. One significant omission relates to the teenage years of David Miscavige, Hubbard’s successor as the head of Scientology, whose plastic smile conceals a ferocious temper.

Wright quotes a comment that Miscavige is alleged to have made about Travolta, whose loyalty to the faith has sometimes wavered: ‘The guy is a faggot. We’re going to out him.’ Surprisingly, that line makes it into the British edition. Perhaps the Church can’t be bothered to defend a celebrity whose sexuality has been questioned so often and so plausibly.

Tom Cruise is another matter. First, there really is no evidence that he’s gay. Second, he is Scientology’s most valuable asset: Miscavige will go to extraordinary lengths to keep him happy. Wright reports Cruise ‘drooling’ over a custom-painted motorcycle the church paid for; there’s an account of 100 Scientology-hired contractors tarting up the actor’s nine-bedroom mansion in Beverly Hills to a grotesque state of luxury. The fawning over Cruise rankles with ex-Scientologists; yet it’s interesting how many want to hold on to aspects of the cult’s teaching even after leaving.

It’s easy to dismiss Scientology as a scam. Hubbard liked to pile $100 bills four feet high and, according to Going Clear, founded religious front organisations to siphon millions into his personal accounts. But he seems to have believed in his eccentric and cruel teachings and so does Miscavige. For that reason Wright takes seriously its claim to be a religion.

But not, however, a successful one. Although there are no official statistics, informally it boasts of eight million members worldwide. Wright argues convincingly that the number of active Scientologists has fallen to around 30,000, a truly pitiful total for such a wealthy organisation. Of all the damning allegations in the book, this is surely the one that will upset the church the most.