Juanita Feros Ruys 
Demons in the Middle Ages [PDF ebook] 

The medieval world was full of malicious demons: fallen angels commissioned to tempt humans away from God. From demons disguised as beautiful women to demons that took frightening animal-like forms, this book explores the history of thought about demons: what they were, what they could and could not do, and how they affected human lives. It considers the debates, stories, and writing that eventually gave shape to the witchcraze of the early modern period.