The Shepherd's Crown: Terry Pratchett

The fifth and final book in the Tiffany Aching series - five Discworld novels by master-storyteller Terry Pratchett.
Tiffany Aching has finally got her wish.
She is a witch (and a respected one, at that). Overworked and underpaid, that`s for certain, but a witch nonetheless.
Help is at hand though. In the form of young Geoffrey and his goat. Geoffrey wants to be a witch too, and thinks he can save the world by building sheds. Well, everyone has to start somewhere.
But as new friends are made, and old ones return, enemies are stirring. With her beloved chalk in jeopardy, Tiffany will face the toughest challenge of her life.
There will be a reckoning . . .