Witches Abroad by Terry Pratchett (Discworld 12)

"Stories don't care who takes part in them. All that matters is that the story gets told, that the story repeats. Or, if you prefer to think of it like this: stories are a parasitical life form, warping lives in the service only of the story itself."

Our favorite coven of witches is back, and they're going to be dealing with the most terrifying thing they've ever encountered, traveling to foreign lands!