King of Ravens (Upon a Broken Throne #1)

He’ll do anything to keep her. She’d do anything to escape.
 
Rhiannon is dying—of what, she doesn’t know. Kept protected by her family in their remote seaside cottage, she spends her days searching for a cure. Her world is torn apart, however, when a fae King of the Dead invades her home.
 
Cold and cruel, Drystan offers her a choice: descend to the underworld as his bride or watch her family die. Trapped in a twisted bargain, Rhiannon is thrust into a world of withered gods, scheming courtiers, and ancient magic, but she refuses to be a pawn in a game she never agreed to play. She attempts over and over to run away, until Drystan offers her a new bargain: escape his deadly labyrinth, and he will set her free. Fail, and become his bride.
 
But in a court where every promise has teeth, Annon must make an impossible choice: return to the home she's always loved or claim her place in a world where she might finally belong.