Abnormally Normal
It goes something like this
The unnamed protagonist, known only as of the boy, moves in with his grandmother after he is left an orphan. The boy and his grandmother are great friends. She tells him many stories about witches, specifically how to recognize them so he will be safe from them. Aside from a few distinguishing physical characteristics (they are bald, have clawed hands, and lack toes), witches look like human women but are awful creatures that prey on children.