This would be a one-star book, except I think there's a pretty good chance I would have loved it when I was a kid. As an adult, though? Tissue-thin worldbuilding, paint-by-numbers plotting "Oh," said I, the moment the protagonist spotted the old beggar in the shop, "that must be the missing king. And look, there's the Designated Love Interest!", and a main character who. . . .
Okay. Actually, I think the main character is the most interesting part of the book, because she is exactly
what you'd expect for someone of her age and background: snobby, oblivious to her privilege, convinced the world revolves around her, and an ass to pretty much everyone she meets. It is a completely convincing portrait of a thoroughly unpleasant individual. And I would have enjoyed reading it if she were cast as an anti-hero--or if the book was about her learning and growing beyond her flaws.
But no, it's protagonist-centric morality all the way down. She is convinced she's the center of the universe because she is
the center of the universe; everyone she meets, even people who should hate her, quickly come to see her for the amazing person she is (except, of course, for the villains, who you can identify because they are ugly, disabled, and the only people to dislike the protagonist).
It's wish-fulfillment for misunderstood tweens. There's a place for that. I ate Mercedes Lackey up with a spoon when I was twelve. But I'm not twelve any more, and this was painful to read.