Witches Abroad is the twelfth novel in Pratchett's phenomenally successful Discworld series.      "Things have to come to an end, see. That's how it works when you turn the world into stories. You should never have done that. You shouldn't treat people like they was characters, like they was things. But if you do, then you've got to know where the story ends."     It seemed an easy job... After all, how difficult could it be to make sure that a servant girl doesn't marry a prince? Quite hard, actually, even for the witches Granny Weatherwax, Nanny Ogg and Magrat Garlick. That's the problem with real life -- it tends to get in the way of a good story, and a good story is hard to resist. Servant girls have to marry the prince. That's what life is all about. You can't fight a Happy Ending, especially when it comes with glass slippers and a Fairy Godmother who has made Destiny an offer it can't refuse.     At least -- up until now...