Throne of Glass by Sarah J. Maas

Famed assassin Celaena Sardothien has spent a year as a slave in the Endovier salt mines as retribution for her crimes. When Prince Dorian offers her eventual freedom, she jumps at the chance. He has one condition: she must act as the prince’s champion to win the position of royal assassin in a competition created by the sadistic King of Adarlan. She must fight against other assassins and thieves in a series of trials that require physical skill, wits, and bravery. If she wins, she’ll serve the kingdom for four years to earn her freedom. That is, if she survives.

When competitors start mysteriously dying one after the other, Celaena must figure out who the killer is before she’s next. What she finds not only changes the competition, but the fate of the kingdom, and her own destiny.

Throne of Glass is an entertaining story on its own, but it’s where the rest of the series goes that really makes the read worthwhile. This is a high fantasy YA series that is quite mature in content and features older characters. They are also turning this series into a television show called “Queen of Shadows” at some point in the future.