Such a shame. This book had so much potential. On a whim, we bought this during a fill-a-bag-for-$3 sale at our library. It looked beautiful (the characters are so cutely drawn) and the idea sounded neat. Well, after reading it at home it's going straight to Goodwill. What a strange book. The Monster Princess had no choice to do anything but accept living underground where she is filthy, covered in fleas, and (originally) unhappy, because she is a monster and monsters aren't supposed to be princesses.
Is this a message you want to send a child? Do you want to be telling your child that if something doesn't work out for them, they should quit? While I'm a believer in being yourself, it's a message that gets pushed on children way too often to the point they give up on dreams and fail to understand that sometimes changing behavior (in positive ways) can help with making friends or fitting in (in the positive sense--not giving up your individuality). It also sends the message you are either beautiful and nasty--or a monster and nice. There was no in between and no decent motivations for the characters' behavior. Anyone who has a clue what it's really like to be "unpopular" and struggle with bullying will know why this is a bad idea.
For positive alternatives to stereotypical princesses, we'll happily read "The Paperbag Princess" or put on "Tangled." And for our beautiful/heroic monster kick, we'll watch "Nightmare Before Christmas" (similar theme, but way better conveyed as the monsters get included in the Christmas celebration at the end rather than shoved back into darkness and solitude).