Dead Queen (Thrones of Ruin #1) by Briar Knightly

A reluctant heir. A deadly secret. A wolf who prowls the shadows of the Fox King's court.

Sienna wants nothing to do with the throne she stands to inherit, but a royal summons drags her away from the war-ravaged borderlands, back into the Fox King's court. Now she's trapped in a palace haunted by her grandmother's mysterious death, and engaged to a man she didn't choose ... even if her charming fiancé is a knight she once loved.

When one of the Dead Queen's Wolves is caught spying in the Fox King's court, Sienna begins to suspect the truth of the war is far darker than she imagined. To uncover buried secrets, she must trust the Wolf and help him escape north, where the ancient Dead Queen reigns over more than the living.

As corpse wolves stalk the borders and rebellion brews, whispers rise of old fae magic and kingdoms long fallen. Sienna must decide if the Wolf at her side is a monster or something much more dangerous.

Because in the north, secrets won't stay buried. And neither will the dead.