The Wicked Years Series Novels

Out of Oz (The Wicked Years 4) by Gregory Maguire
A Lion Among Men (The Wicked Years 3) by Gregory Maguire
Son of a Witch (The Wicked Years 2) by Gregory Maguire
Wicked: The Life and Times of the Wicked Witch of the West (The Wicked Years 1) by Gregory Maguire