A Hat Full of Sky (by Terry Pratchett)

But there's a strange, invisible creature called a Hiver that's after Tiffany. Drawn by her growing power, it lives by taking over the bodies of powerful sorcerers, and only the Nac Mac Feegle know it's coming. But the new Kelda, jealous of Tiffany, doesn't want to let them leave the Chalk to rescue her.

This sequel is very entertaining, humorous, and moves along quite nicely. But it lacks the rollicking action and broad slapstick humor, both physical and verbal, of its predecessor. Mostly what it lacks is enough of the Feegles. Whenever these drinking, stealing, fighting pictsies are on stage, the fun picks right up. One group of children having The Wee Free Men read to them cheered every time the Feegles appeared in the story. But here they're missing from whole great swaths of the book, and the reader misses them.