I have nothing but good things to say about this book. I really can't think of anything that I found wrong with it. When it comes to the things I love about it, well, that's another story.
I loved that this story wasn't afraid to lead its heroine down a dark path. Eona dipped her toe into the pool of greed, lust, and ambition, and actually wanted to stay there for a while, which is not at all something common for the young adult fantasy genre (where the heroines are steadfastly virtuous at all times). This wasn't a rose-tinted view of a girl immersed in the affairs of a kingdom at war -- difficult decisions of immediate consequence are made, loyalties are constantly questioned, and some very dear characters die. Not even love was kept entirely pure from the taint of politics. The book had so many interesting things to say about power and pawns, which gave the romance another wonderful level. I didn't hate anyone at all in this book, except perhaps Sethon, whose only misfortune was to be cast as a two dimensional villain.