The Ninth Gate is a 1999 mystery thriller film directed, produced, and co-written by Roman Polanski. An international co-production between the United States, Portugal, France, and Spain, the film is loosely based upon Arturo Perez-Reverte's 1993 novel The Club Dumas. The plot involves the search for a rare and ancient book that purportedly contains a magical secret for summoning the Devil. The premiere showing was at San Sebastian, Spain, on 25 August 1999, a month before the 47th San Sebastian International Film Festival. Though critically and commercially unsuccessful in North America, where reviewers compared it unfavorably with Polanski's supernatural film Rosemary's Baby (1968), The Ninth Gate earned a worldwide gross of $58.4 million against a $38 million budget.

What's the best answer to this question: was the ninth gate based on a book?
yes