a black paperback with some satanic symbolism

Necronomicon

A weird, magickal work based on the fictional ideas of H.P. Lovecraft and Alestair Crowley, as well as on some dubious ideas about Middle Eastern mythology as well as the polarities of good and evil. It's part recipe book for summoning demons and such, and part a sort of story-within-a-story-within-a-story about the discovery of ancient, horrific rituals and incantations, which are included in the text, and which you're also warned not to actually use because you could release some really unpleasant arcane forces. Also, some of them involve human sacrifice, so you know what you're getting into. There are several books (both fictional and actually published) by this name; this one is the Necronomicon written by an anonymous person, introduced by someone known only as "Simon;" so it's technically called the Simon Necronomicon.