HBO Scientology film proves popular.

Byline: David Bauder

NEW YORK -- If the Church of Scientology was hoping that HBO's withering documentary on the religion's practices would pass by with little notice, that turned out to be a miscalculation.

"Going Clear: Scientology and the Prison of Belief'' has been seen by more than 5.5 million people since its debut two weeks ago. It is likely to wind up being second only to a 2013 movie on Beyonce as the premium cable network's most-watched documentary of the past decade, HBO said Monday.

It has been an extraordinary two months for HBO's film unit. The six-part series on billionaire Robert Durst, "The Jinx,'' was a sensation with its climax reaching nearly 5 million viewers. Durst was arrested for murder on the eve of the series' last episode, in part due to evidence uncovered by the filmmakers.

The Church of Scientology ran a full-page advertisement in The New York Times denouncing the film before it ran, questioning whether "Going Clear'' would turn out to be like Rolling Stone magazine's since-retracted story about an alleged sexual assault at the University of Virginia.

"I didn't think we expected this kind of noise and this kind of energy, but we'll take it,'' said Sheila Nevins, the veteran chief of HBO's documentary unit. "I didn't think it would be this controversial.''

Director Alex Gibney made "Going Clear,'' based on the book by Lawrence Wright. Gibney also did "Mea Maxima Culpa: Silence in the House of God,'' an investigation into sex abuse in the...