Deliver Us from Evil is the first book to introduce demonologists Ed and Lorraine Warren and their unique occupation as ghost hunters to the world. The Warrens are known as the original ghost hunters. Together they've been investigating paranormal activity for over fifty-five years throughout the United States, Canada, Mexico, Scotland, and Europe, to name only a few places.

This book is not entirely about exorcism and many of these stories do not conclude with happy endings. Lorraine describes the existence of supernatural forces and how these supernatural events follow a certain pattern. Ed says it's best described as a book that teaches you about the reality of paranormal or supernatural forces rather than citing an easy route to deliverance. The title of the book is a phrase taken from the Lord's Prayer - "Lead us not into temptation, but Deliver Us from Evil." The case studies chronicled in this book are a kind of universality of evil spirits, how they operate and what they do.

The cases in this book are the first published cases taken from the files of Ed Warren, a demonologist, now deceased, and his wife, Lorraine Warren, an active clairvoyant and medium. These paranormal investigations are filled with tragic possessions, ghostly infestations and demonic obsessions. Ed, who is also an exorcist, does not ignore the potential potency of curses, spells, voodoo dolls, cult ceremonies, demon possession or other invading entities, especially for those who have opened themselves up to supernatural infestation. Although rare, some satanic rituals have led to murder or death.

From a psychic researcher's point of view, Lorraine points out how spirits move from infestation, the first stage and signs of ghost and/or spirit haunting (knocking, magic whispering and creeping sounds), the mildest state (shadow ghosts and teleportation of objects), to the more dangerous obsession and finally, the last and worse stage, possession. The only difference between obsession and the last stage, possession, is one of degree. Ed describes these experiences in an entirely no-holds-barred way. If you study these stories and these phenomena carefully, you find that one opens the door to infestation, obsession and possession by careless fixation on the occult, playing with the Ouija board and toying with Satanism or black magic.

The most dangerous game and archetypical connection is the Ouija board. According to Ed, "This object, often regarded as a harmless toy, is the way that ordinary people are often lured into making a dangerous connection to the other world." Of the fourteen cases discussed, five are initiated by contact with an Ouija board.

The Warrens have tenaciously pursued their careers as ghost hunters for so many years and witnessed people that have been tragically affected by apparitions, ghost whisperings, brutal and unexplained explosions, strange footsteps in the night, uninvited incursions into the privacy of their bedrooms, including various physical attacks. All cases in this book are prior to 1973. Since the first publication, the Warrens have become known worldwide because of supernatural investigations such as West Point Military Academy, the Amityville Horror murder, the Haunting in Connecticut, the Brookfield Demon Murder, Jack and Janet Smurl, Dudley town, Bill Ramsey the Werewolf, and the Enfield Poltergeist, to name a few. Lorraine appears on A&E's Paranormal State TV series.