Far too long and meandering for the story it is telling, Wicked starts off with a great premise, has an interesting first half and finale. It also has a ponderous middle that could have been cut, tightening up the narrative, without costing the story or characters much.
Also, while not completely surprising given that this is a "re-imaging" of the villain of the Wizard of Oz, ever character has a host of post-modern flaws. There simply are no heroes in the book. Call me simplistic, but on occasion I tire of the dysfunctional narrative, where everyone is wretched, weak and wanting.
Still, there are clever bits and the writing style is engaging, particularly for a book of this length. I read it in the context of a book club, which is probably the best way to do so as it did lead to a nice long discussion.