The Witches by Roald Dahl

This is not a fairy tale. This is about real witches.

Grandmamma loves to tell about witches. Real witches are the most dangerous of all living creatures on earth. There's nothing they hate so much as children, and they work all kinds of terrifying spells to get rid of them. Her grandson listens closely to Grandmamma's stories—but nothing can prepare him for the day he comes face-to-face with The Grand High Witch herself!