Diane Zahler's The Thirteenth Princess retells the story of the twelve dancing princess, but adds an extra as our viewpoint character. The last princess incurred her father's wrath by being first, another girl, and unsurprisingly, one birth too far for the poor mother, who expired on the spot. So Zeta not only doesn't get an A-list name, she is also sent to the kitchen to grow up with the servants instead of among her pampered older siblings.
Luckily this gives her the chance to wander the forest and meet helpful witches and stable boys and soldiers, so when the twelve blond princesses -- our Zeta is a redhead -- start wasting mysteriously away, someone can go for help. I liked how pieces of the fairy tale stay unobtrusively; there is drugged hot chocolate to put Zeta to sleep, the trap-door in their room is a forgotten dumb-waiter that Zeta has been using to visit her sisters from the kitchen, the elder sister gets to marry a soldier (although he isn't quite grizzled, albeit for a twelve year old reading the book there probably isn't much difference between 27 and 63). Also, the princesses are trapped in a spell, not sneaking out in glee, and their dad has grown bitter over the years with the lack of an heir and the death of his wife, which even he has to admit was mostly his fault.
It's a fun retelling, not incredibly rich but not annoyingly shallow. I liked how Zeta didn't put on trousers and start swinging a sword; she's a good cook and determined to save her sisters but isn't magically perfectly brave and heroic. This book inspires me to consider the A-Z challenge again, because look -- a Z author! B