A Book of Shadows (BOS) is a personal, varied compilation documenting a witch's beliefs, practices, rituals, and spells. Originating in the 1940s-50s by Gerald Gardner, it has gained popularity and can be used as a detailed journal or a textbook. Styles and uses vary significantly depending on the individual and their needs, and traditions surrounding a BOS differ widely. Though beneficial, it is not deemed necessary for practicing witchcraft.