A retelling of the fairy tale The Twelve Dancing Princesses.
I think that if I had not previously read "Entwined" by Heather Dixon, another retelling of the same tale, I would have enjoyed "Princess of the Midnight Ball" better. Where "Entwined" melded the fairy tale with a Jane Austen book and had loads of interesting and well-rounded characters, "Princess of the Midnight Ball" was pretty much a straight retelling of the original tale, with no clever variations and very, VERY little character development.
Much like it's main character, the young soldier Galen Werner, the book was pleasant and rather bland. Not a bad book by any means, just an adequate one.