House of flame and shadow / Sarah J. Maas.

Bryce Quinlan never expected to see a world other than Midgard, but now that she has, all she wants is to get back. Everything she loves is in Midgard: her family, her friends, her mate. Stranded in a strange new world, she's going to need all her wits about her to get home again. And that's no easy feat when she has no idea who to trust. Hunt Athalar has found himself in some deep holes in his life, but this one might be the deepest of all. After a few brief months with everything he ever wanted, he's in the Asteri's dungeons again, stripped of his freedom and without a clue as to Bryce's fate. He's desperate to help her, but until he can escape the Asteri's leash, his hands are quite literally tied. Midgard is brought to the brink of collapse, and the fate of the world rests on the hope of rebellion. But the fight for survival, freedom and love may cost everything Bryce and Hunt have.