The Iron Vow by Julie Kagawa

The extraordinary finale to Julie Kagawa’s New York Times and internationally bestselling Iron Fey series is here…and the fate of the Nevernever and all the world hangs in the balance. Join Meghan, Ash, Puck, Grimalkin, and the entire Iron Fey cast for this final epic journey into worlds where imagination knows no boundaries…
After leaping through the portal to Evenfall, Meghan and her companions find themselves in a terrifying new world where Nightmares roam and glamour is nearly nonexistent. As their magic wanes and the creatures of Evenfall rise against them, the race to find the Nightmare King grows ever more desperate. But what they discover—about Evenfall, about the Nightmare King, about themselves—will shake everything they thought they knew to the core.

The Nightmare King stirs. A world hangs in the balance. And as twilight descends upon all the realms of Faery, Meghan and her allies must make one more impossible choice.