What is a BOS? A Book of Shadows contains the specific beliefs of an individual or group of individuals who practice the traditions of Wicca or Witchcraft.. Today some choose to purchase a Book of Shadows written by another practitioner, and simply follow the author’s instructions for circle casting, the consecration of tools, religious rituals, coven organization, initiation ceremonies and more. This article is for those who prefer to create their own Book of Shadows and keep the contents private.