It's interesting to know that The Wonderful Wizard of Oz is only one book in a series of Oz Books written by Frank Baum. Not so unlike other series collections like Harry Potter, Narnia, or LoTR, Baum's books build up a fictitious world, Oz. Each of Baum's books focus on different characters in the initial book with titles like Glinda of Oz, The Tin Woodsman of Oz, The Scarecrow of Oz, and more.
To me, Oz doesn't have the same appeal as Middle-Earth or even Narnia, but Gregory Maguire's version creates something that none of the other fictional worlds do, a second telling of how things really were. As anyone that has read the book or seen the musical knows, it turns the initial story on its head and adds depth to a fiction that was somewhat flat. The new Disney version, though not as brave in its retelling as Wicked, picks up on this as well.
Notice that the "Tik-Tok" robot used in Wicked, has its own Oz book below.
