The Prisoner's Throne - Holly Black

Prince Oak is paying for his betrayal. Imprisoned in the icy north and bound to the will of a monstrous new queen, he must rely on charm and calculation to survive. With High King Cardan and High Queen Jude willing to use any means necessary to retrieve their stolen heir, Oak will have to decide whether to attempt regaining the trust of the girl he’s always loved or to remain loyal to Elfhame and hand over the means to end her reign—even if it means ending Wren, too.

With a new war looming on the horizon and treachery lurking in every corner, neither Oak’s guile nor his wit will be enough to keep everyone he loves alive. It’s just a question of whom he will doom.