THRONE OF GLASS (Sarah J. Maas)

In the dark, filthy salt mines of Endovier, an eighteen-year-old girl is serving a life sentence. She is a trained assassin, the best of her kind, but she made a fatal mistake. She got caught. Crown Prince Dorian offers eighteen-year-old assassin Celaena Sardothien her freedom on the condition that she act as his champion in a competition to find a new royal assassin. Celaena must represent the prince in a to-the-death tournament - fighting the most gifted thieves and assassins in the land. Live or die, Celaena will be free. Win or lose, she is about to discover her true destiny. But will her assassin's heart be melted?

If she beats her opponents in a series of eliminations, she'll serve the kingdom for three years and then be granted her freedom. 

Celaena finds her training sessions with the captain of the guard, Westfall, challenging and exhilirating. But she's bored stiff by court life. Things get a little more interesting when the prince starts to show interest in her... but it's the gruff Captain Westfall who seems to understand her best. 

Then one of the other contestants turns up dead... quickly followed by another. 

Can Celaena figure out who the killer is before she becomes a victim? As the young assassin investigates, her search leads her to discover a greater destiny than she could possibly have imagined