Là-Bas

Also known as Là-Bas (Down There) and The Damned.

At the novel's center is Durtal, a writer obsessed with the life of one of the blackest figures in history, Gilles de Rais - child murderer, sadist, necrophile, and practitioner of all the black arts. The book's authentic, extraordinarily detailed descriptions of the Black Mass have never been surpassed.