While the supporting characters were a tad stereotypical and predictable, overall this book is a big win. Shelved by my library as YA (perhaps since the main character is 12), this book seems more suitable for the younger end of the "Middle grade" audience.
Reading as an adult, I predicted the big twist about 1/3 of the way through. It will be interesting to see if my fantasy obsessed, precocious reader son (currently in 3rd grade) also predicts the big reveal.
I can see why people compare The False Prince to The Thief by Megan Whalen Turner. Of the two, I prefer The False Prince.