"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."
The Tiffany Aching series are young adult Discworld novels, with Pratchett's wonderful blend of wacky fantasy and tongue-in-cheek humour. Tiffany Aching is an inspiring female character, too! They would be great on Yoto cards. The whole series include:
The Wee Free Men
A Hat Full of Sky
Wintersmith
I Shall Wear Midnight
The Shepherd’s Crown
Audiobooks has a version read by Stephen Briggs; there are also several audio versions on Amazon (one by Tony Robinson, another read by Indira Varma, Bill Nighy and Steven Cree).