Kingdom of Ash Book by Sarah J. Maas

With Aelin captured, Aedion and Lysandra remain the last line of defense to protect Terrasen from utter destruction. Yet they soon realize that the many allies they’ve gathered to battle Erawan’s hordes might not be enough to save them. Scattered across the continent and racing against time, Chaol, Manon, and Dorian are forced to forge their own paths to meet their fates. Hanging in the balance is any hope of salvation-and a better world.

And across the sea, his companions unwavering beside him, Rowan hunts to find his captured wife and queen-before she is lost to him forever.

As the threads of fate weave together at last, all must fight, if they are to have a chance at a future. Some bonds will grow even deeper, while others will be severed forever in the explosive final chapter of the Throne of Glass series.