Good news for those who were disappointed that Paul Thomas Anderson's The Master turned out to be a vague parable of Scientology rather than a penetrating exposé of it: a new book promises to do the job instead. Just the title of Lawrence Wright's Going Clear: Scientology, Hollywood and the Prison of Belief tells you more than The Master did. Going Clear is a veritable book of revelations on L Ron Hubbard's sci-fi religion, exhaustively detailing its history, its methods and the depth of its weirdness.

Or so we're told. While Going Clear goes on sale in the US and the rest of Europe this week, you can't buy it in Britain. Not because it threatens national security, or features royal breasts, but because of our uniquely obliging libel laws.

Unlike in other countries, under English and Welsh law the burden of proof in defamation cases rests exclusively on the defendant, which means that if someone sues you, it's up to you to prove that it's true. If that someone is, say, a pharmaceutical company, or a church that believes in space people, then you're in for a long, expensive time in court, even if you win (legal costs here are up to 140 times higher than international norms). Hence Transworld's decision not to publish. The legal advice was that Going Clear's content was "not robust enough for the UK market," they say.

"It's a classic example of the chill that is cast over free speech by these laws, where people choose to self-censor," says Robert Sharp, head of campaigns and communications at the human rights organisation English PEN. "Something like religion is in the public interest. We should be allowed to scrutinise and criticise it. The cover-up of abuses by the Catholic church is a prime example of what happens when you don't."

Going Clear isn't the first Scientology-related book to be shelved in this country. In 2008, British booksellers were warned off selling John Duignan's insider account The Complex. John Sweeney recently tweeted that his current Scientology book, Church Of Fear, was "nixed by all big UK publishers". The good news is that PEN and other free-speech groups have been campaigning for libel reform since 2010, and we could see changes when parliament debates the defamation bill this week.