The book was written by Jacques Auguste Simon Collin de Plancy and published 1818. De Plancy was an atheist, a friend and contemporary of the rationalist Voltaire. The first edition was described as “… a Universal Library on the beings, characters, books, deeds, and causes which pertain to the manifestations and magic of trafficking with Hell; divinations, occult sciences, grimoires, marvels, errors, prejudices, traditions, folktales, the various superstitions, and generally all manner of marvellous, surprising, mysterious, and supernatural beliefs.” De Plancy believed at the time he wrote the first edition that the church conncocted stories of demons and hell to scare people into believing.
By the time the 6th edition of the popular book came out in 1863 de Plancy, much to the dismay of his collegues, had become a devout catholic. He commissioned artists to create 550 illustrations of the creatures the book describes. Usually the first edition of a book is the most valuable. In this case, the 6th edition is by far the most sought after.