This volume investigates the historical and theological development of diabolism and witchcraft through the lens of traditional occult scholarship. Montague Summers, a noted 20th-century scholar of the macabre and religious history, compiles a comprehensive analysis of primary source materials and historical accounts. He argues that these phenomena are not merely folklore but represent a persistent, tangible influence within the historical and spiritual framework of Western civilization.

Scholars and enthusiasts of occult history recognize this work as a significant, albeit highly subjective, collection of primary source material. Readers frequently note the dense, archaic prose style that reflects the author's specific early 20th-century academic perspective.