Terry Pratchett 
Wee Free Men 

The first in a series of Discworld novels starring the young witch Tiffany Aching.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 Feegleaka the Wee Free Mena 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. . . .