Drago Descending by Greg F. Gifune (2006-11-01)

Private Investigator David Drago is a former policeman and Gulf War veteran struggling with his combat experiences, his time spent in the psychological ward of a veteran's hospital, and the darkness of his past. When he is approached by a mysterious client who hires him to locate his missing fiancé, Jesse Greenlaw, Drago hesitantly takes the case. The problem, Jesse is also David's former girlfriend, and an integral part of the murky past still haunting him. Drago's investigation leads him into a labyrinth of violence, sexual intrigue, black witchcraft, and Satanism. The deeper he digs, the deeper he descends into a dark netherworld haunted by terrifying visions of angels and demons alike.