The Shadows Between Us by Tricia Levenseller

Alessandra is tired of being overlooked, but she has a plan to gain power:

1) Woo the Shadow King.
2) Marry him.
3) Kill him and take his kingdom for herself.

No one knows the extent of the freshly crowned Shadow King’s power. Some say he can command the shadows that swirl around him to do his bidding. Others say they speak to him, whispering the thoughts of his enemies. Regardless, Alessandra knows what she deserves, and she’s going to do everything within her power to get it.

But Alessandra’s not the only one trying to kill the king. As attempts on his life are made, she finds herself trying to keep him alive long enough for him to make her his queen—all while struggling not to lose her heart. After all, who better for a Shadow King than a cunning, villainous queen?