Some confusion exists as to whether The Demonologist and The Exorcist are related. They are not. Although both books treat the same subject matter, they do so in a different way. One is a novel, the other is nonfiction. Where the simil- arity resides, beyond their respective titles, is that both books were developed somewhat simultaneously in the late 1960s and 70s, and both focus on the topic of religious demonology. Both authors were also lent encouragement by the late Jesuit priest and scholar Malachi Martin, author of Hostage To The Devil.
The Exorcist tells, with considerable accuracy, the true-life story of a young Maryland boy, Douglas Dean, who experienced a rather ferocious case of diabolical possession in 1949 and details the progression of the boy's travail in novel form. While The Exorcist is based on an actual event, the book confines itself almost excusively to the possession phase of the phenomenon. The Demonologist concerns itself with the same material, but does so in a nonfiction manner, though it takes the subject one step further and unfurls the dynamics behind all three stages of diabolical phenomena. In the end, rather than competing, both books complement each other instead.
For those seeking to gain a comprehensive grasp of the subject, one should read all three books, The Demonologist, The Exorcist, and Hostage To The Devil - in that order. The Demonologist first explains how the phenomenon occurs; The Exorcist then shows that phenomenon taking place in a real life situation; and finally, Martin's Hostage To The Devil - though denser and more academic in nature - drives home the consummate awe and despotic cruelty of the inhuman demonic spirit.
