With more than 400 entries and 80 black-and-white photos, this resource explores what many believe are the sources of evil—demons or devils. Demons, as defined here, are “lower agents of evil,” having many guises and operating under many names with many purposes. The book does a fine job of walking the reader through all the mythology; if readers are looking for a strictly Christian interpretation of demonology, it’s not here. Key topics include the types of demons and history of demonology, possession and historical cases, today’s demonologists and exorcists, forms and means of confronting demons, and demons in popular culture, different cultures, and many religious traditions. Entries are organized A–Z, and most conclude with a short title list of further reading. Additionally, a concise, unannotated bibliography is included at the end of the work. Guiley is a leading authority and author on numerous paranormal topics and has appeared on TV and radio shows. She feels everyone needs to be informed about demons, and with this title, she wants to “open further avenues of inquiry on the subject of the dark side.” The work is a thorough reference on an arcane subject and is valuable for its many historical accounts of demons or devils and their arts. Guiley is sometimes criticized for her lack of skepticism, but she has produced a helpful resource for readers who need an overview. It will be used in public and academic libraries by patrons who are interested in demonology.