Throne Of Glass: Sarah J. Maas

In a land where magic has vanished, a cruel king rules from a throne of glass. 

Eighteen-year-old Celaena Sardothien is a legendary assassin. She is serving a brutal life sentence in the salt mines of Endovier. 

The Crown Prince offers her a chance at freedom. She must enter a deadly competition to become the King's Champion. She needs to defeat twenty-three killers, thieves, and warriors. 

But as her competitors start dying mysteriously one by one, her fight for freedom turns into a desperate fight for survival. She must uncover a dark evil lurking inside the glass castle before it destroys her entire world.