A Hat Full of Sky (Discworld #32)

Tiffany Aching, a hag from a long line of hags, is trying out her witchy talents again as she is plunged into yet another adventure when she leaves home and is apprenticed to a real witch. This time, will the thieving, fighting and drinking skills of the Nac Mac Feegle the Wee Free Men be of use, or must Tiffany rely on her own abilities?

This is the third novel in the junior Discworld series that started with the enormously popular tale:The Amazing Maurice and His Educated Rodents.