kingdom of Ash, by Sarah J. Maas.

Years in the making, Sarah J. Maas’s #1 New York Times bestselling Throne of Glass series comes to an epic, unforgettable conclusion. Aelin Galathynius’s journey from slave to king’s assassin to the queen of a once-great kingdom reaches its heart-rending finale as war erupts across her world. Aelin has risked everything to save her people — but at a tremendous cost. Locked within an iron coffin by the Queen of the Fae, Aelin must draw upon her fiery will as she endures months of torture.

As Aelin languishes in captivity, Aedion and Lysandra emerge as Terrasen's final bastion against annihilation. However, their daunting task reveals a harsh truth: the coalition amassed to combat Erawan's forces may prove insufficient. With allies dispersed and the clock ticking ominously, Chaol, Manon, and Dorian find themselves compelled to chart separate courses toward destiny. The fate of their world, and the prospect of a brighter future, teeters precariously, balanced on a knife's edge.