Queen of Shadows- Sarah J. Maas

Celaena Sardothien has embraced her identity as Aelin Galathynius, Queen of Terrasen. But before she can reclaim her throne, she must fight. She will fight for her cousin, a warrior prepared to die for her. She will fight for her friend, a young man trapped in an unspeakable prison. And she will fight for her people, enslaved to a brutal king and awaiting their lost queen's triumphant return.