Celilia is just an average, everyday peasant who spends most of her day doing chores and scrubbing the stains out of her pinafore. At least, that is what she wants everyone to THINK she is. What no one sees is that she studies at night books on royal protocol, history, and the royal family...
Yes, Celilia is actually a princess-- the princess! The only problem is that the same people who killed her parents when she was a baby are still seeking to steal the throne. So a decoy princess is on the throne while Celilia is in hiding.
However, Celilia is tired of waiting to take her throne. Nothing has happened all these years, and Celilia believes she is ready.
So with her best friend Harper, Celilia sets out to claim what is rightfully hers. Only, when they get to the castle, there are a few small problems... okay, big, huge complications!! The decoy princess believes a totally different story!
"Palace of Mirrors", a roundabout sequal to Haddix's earlier book "Just Ella", is worth reading. In fact, it is worth rereading! The cool thing is, you don't have to have read "Just Ella" to understand what is going on, though it does help to know who Ella Brown is.
Personally, though I really liked the book, I did not think it was one of Ms. Haddix's best. I much prefer her Shadow Children series, Double Identity, Running Out of Time, and Uprising.
That is not to say that this book is not super good, because it is! Only, if you do read this book, be sure to read her others too, because they are better.