This is my favorite of the wicked cycle, excluding wicked itself. All of the books are wonderful and have their own stories to tell and main characters, but this book is the best for both tying it together and pulling it apart. One of my main problems with the wicked books is that there is a great deal of random stuff tossed in especially surrounding Elphaba herself. You're given promises and hints that she is 'coming back' through the entire series. This is the first time where you are set free of that shackle and allowed to really enjoy the book as a stand alone.
While I love all of these books and Gregory Maguire, I honestly think that this is the best of the lot, which is nice considering it's also the last.