The Wee Free Men (Terry Pratchett)

Summary: A nightmarish danger threatens from the other side of reality...

Armed with only a frying pan and her common sense, young witch-to-be Tiffany Aching must defend her home against the monsters of Fairyland.  Luckily she has some very unusual help: the local Nac Mac Feegle--aka the Wee Free Men--a clan of fierce, sheep-stealing, sword-wielding, six-inch-high blue men.

Together they must face headless horsemen, ferocious grimhounds, terrifying dreams come true, and ultimately the sinister Queen of the Elves herself... (from amazon.com)

Where can I find it?: Boston Public Library: Codman Square, Copley, Fields Corner, Honan-Allston, Jamaica Plain, and West Roxbury branches, or as an ebook at https://bpl.bibliocommons.com/v2/record/S981C13095699

Tags: Discworld (Imaginary place); Fairies; Witches; Aching, Tiffany (Fictitious character); Brothers and sisters; Magic