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 ready to use any means necessary to retrieve their stolen heir, should Oak attempt to regain the trust of the girl he's always loved, or remain loyal to Elfhame and hand over the means to end her reign - even if it means ending Wren too... With war looming and treachery lurking in every corner, neither Oak's guile nor his wit will be enough to keep everyone he loves alive. He will have some terrible choices to make.