The ninth gate film is based, very truthfully, on a half of the plot of the novel “The Dumas Club” by Arturo Pérez Reverte. In my opinion, the other half of the plot, where Lucas (Dean in the film) Corso is searching for an incunable (first edition of a lost chapter of the Three Musketeers) is much better than that one of the demonic books of the Ninth Gate of Hell.