he description of the Necronomicon states that the book is dangerous to read, because it can harm the physical and mental health of the reader. For this reason, the book is kept under seven locks in libraries. The Necronomicon contains occult knowledge, magical rituals, spells, information about sorcerers , the undead , demons , the Afterlife , as well as the Ancient Gods and extraterrestrial beings from Other Worlds, and other dark matters. The Necronomicon is the most famous book in the Cthulhu Mythos .