Crown of midnight by Maas, Sarah J.

18-year-old Celaena Sardothien is bold, daring and beautiful – the perfect seductress and the greatest assassin her world has ever known. But though she won the King’s contest and became his champion, Celaena has been granted neither her liberty nor the freedom to follow her heart. The slavery of the suffocating salt mines of Endovier that scarred her past is nothing compared to a life bound to her darkest enemy, a king whose rule is so dark and evil it is near impossible to defy. Celaena faces a choice that is tearing her heart to pieces.