Authorship is attributed to the occultist Henry Cornelius Agrippa, but the book, supposedly the fourth volume of Agrippa’s monumental three-volume Occult Philosophy, was written by an unknown author. It is also known as the Liber Spirituum and is in the opening of the Lemegeton. The Fourth Book appeared after the death of Agrippa in 1535 and rehashes in an informal way much of the material in Occult Philosophy. Weyer, a student of Agrippa, rejected it as a forgery, as did other occultists.
As the Lemegeton does, the Fourth Book gives instructions for communicating with evil spirits. It covers the names of spirits associated with the planets and their characters, sigils, and pentacles. There are rituals for evoking both good and evil spirits and for practicing necromancy. Waite called the Fourth Book “muddled” and said its lack of precision rendered it ineffective as a manual of magic.