I'm told The Demonologist has been somewhat of a cult item in the United States for the last twenty years. On the surface it tells the life story of America's most famous ghosthunters, Ed and Lorraine Warren, but once you actually get into it, the book quickly gets into the business of telling you how and why mystical phenomena occur. Yes, the subject is deep, but it's presented in an understandable progression and provides just enough theological explanation to scare you right down to the soul. You could read a dozen books on this subject, but once you read this one you won't need (or want) to read another. It has honestly changed my perception of life and I recommend it to anyone who really wants to know the big picture.