Wintersmith - Terry Pratchett
It's Terry Pratchett. You've already made up your minds.
(I think he's worn himself a deep grove with the Discworld books, and now that he knows how to write a Discworld story, he can't not write it that way. I've read this before. It's still a good book, and Tiffany Aching brings all sorts of New and Refreshing to the witches. Me & sensible 13 year old witches = <3)