Shani Oates comes two important conclusions in this beautiful book about the devil, witches and the sabbat: Don't confuse witchcraft and the attribution "witch" with craft as in "practice". Furthermore, at the heart of craft and custom lies a form of comunal feast which we know as sabbat.
This is not a history of the devil, as some might think. It isn't a philosophical or theological treatise either. And while the first is not mandatory, the latter might be quite useful in light of difficult ontological questions which she raises despite the premise to remain solely on historical grounds: What do we do with magic as "illusion", as she professes? What's the devil after all, being a chimaira concocted by the curch?