Wicked: The Life and Times of the Wicked Witch of the West
by Gregory Maguire
Miss Greyling is the sorcery teacher at Shiz. She's very young and overly enthusiastic, but it's under her tutelage that Glinda starts developing her own considerable talent in sorcery. Miss Greyling also leads some interesting discussions on the merits of magic over science, which prompts Glinda and Elphaba to continue the debate over lunch one day.