Queen of Shadows by Sarah J. Maas

Throne of Glass, book 4

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.

Everyone Aelin loves has been taken from her. Everything she holds dear is in danger. But she has the heart of a queen, and that heart beats for vengeance.

In this fourth book in the #1 bestselling Throne of Glass series, no one will escape the queen's wrath.