Seriously, no, the book doesn't exist. Most books that are said to be ancient and evil generally aren't, like the Necronomicon. Though the movie Ninth Gate involves this 'mystical' tome and shows it several times in the film, the only place it was ever printed was in a studio's prop department.
The movie, however, is based on a real book. It is called The Club Dumas, by Arturo P�rez-Reverte. (Sonia Soto has tranlated it for those of us who don't speak Spanish.) You can still order that at a retail bookstore. Of course, the Ninth Gate is out on DVD and all that, too.