The Princess Curseby Merrie Haskell is officially released today. I've lost count of how many Twelve Dancing Princesses themed novels we've seen in the past decade. This is one of the only ones aimed primarily at middle readers however. I really like the cover art on this one.
Book description from the publisher:
Twelve princesses suffer from a puzzling (if silly) curse, and anyone who ends it will win a reward. Reveka, a sharp-witted and irreverent apprentice herbalist, wants that reward. But her investigations lead to deeper mysteries and a daunting choice—will she break the curse at the peril of her own soul? Ages 10 and up.