Stories have power, they are well worn narrative paths through life that it is impossible not to follow. But that can be changed. Stories have to start somewhere, and some people are catalysts that cause stories to begin. The Lancre witches are such a group. Magrat is suddenly a fairy godmother, on recieving a fairy wand when it's owner dies, although she recieves no instructions and it tends to revert to pumpkins. She has to got to Genua (think New Orleans with attitude) to prevent the princess marrying someone she'd hate. Nanny Ogg and Granny Weatherwax tag along too. They cause a number of villages across the continent to revise their beliefs and encounter a number of well trodden storybook paths. It takes a special person to cause stories to happen, and a powerful witch sits at the centre of the storm. It also takes a special kind of person to change the course of narrative, and put a cog in the wheels of the story. They stand face to face at the end and a new story is born. Stories don't care if the people are happy, its the ending that matters.