Mysteries of the Unknown is a series of books about the paranormal, published by Time-Life Books from 1987 through 1991. Each book focused on a different topic, such as ghosts, UFOs, psychic powers and dreams. Book titles included The UFO Phenomenon, Witches and Witchcraft, Hauntings, and more. The idea for the series was conceived following the popularity of the publisher's previous Enchanted World book series. The Mysteries of the Unknown series used scientific aspects for credibility of its theories. The books broke the sales record for the company.

Time Life, is an American company formerly known for its production company and direct marketer conglomerate known for selling books, music, video/DVD, and multimedia products. The current focus of the group is music, video, and entertainment experiences as the Time Life book division closed in 2001. Its products have been sold throughout North America, Europe, Australia, and Asia through television, print, retail, the Internet, telemarketing, and direct sales. Current operations are focused in the US and Canada with limited retail distribution overseas.