I finally finished Wicked, probably the last person on the planet to actually read this. I liked it, mostly. I guess I had some preconceptions, having gotten to know the soundtrack first, but it satisfied.
My only quibble - its seems like in the later chapters, there was a bit of a scramble to try to assemble the pieces to tie in with the Baum works - I confess to never having read the Oz books and only basing my connection on the movie, so I am limited. But it seemed to me as if the transformation from this sort of angry but romantic young woman to the proto witch was forced, and that I wanted Elphie to be a bit more aware of and challenged by her power - it seemed to me that she was more of a spectator in her own life.
I do think I need to read the Oz books.