Falling Angel by William Hjortsberg
Filmed as Angel Heart by Alan Parker
An outstanding, spellbinding novel of murder, mystery and the occult, Falling Angel pits a tough New York private eye, Harry Angel against the most fearsome adversary a detective ever faced - one Louis Cyphre. For Angel a routine missing-persons case turns into a fiendish nightmare of voodoo and black magic, of dizzying peril and violent death - a world in which the shadow he chases seems to be the shadow he casts.