I just watched the TV movie adaptation of Confessions of an Ugly Stepsister by Gregory Maguire. I was surprised by how faithful the movie was to the book; although it leaves off some of the darker aspects of the plot, such as Margarethe poisoning Henrika and the 'gallery of God's mistakes', overall the plot follows very closely and there was even a little dialog that I think was taken right from the book. (It ends on a happier note, too -- although sometimes I think Maguire ended the book the way he did just because he likes being depressing.) It's certainly closer to the source material than the musical Wicked.
Anyway. I caught a bit of it, halfway through, on TV, and hunted down the whole thing online. If you have 90 minutes or so to kill, have a go at it :)