Dark Sun by Melissa Marr

When the bestselling WICKED LOVELY series ended, the Faery Courts were in order. In the years following, peace was still tenuous, but every court seemed devoted to balance.

But now, Urian—son of the former Dark King and the fated Summer Queen, Thelma Foy—has decided to claim his destiny.
Urian knew the secrets that protected his relatives–both the mortal and the faery ones–since childhood. After the Summer Queen claimed the throne that should have been his mother’s and a lowly advisor claimed the throne that was his father’s, Uri is done hiding. The Dark Summer Prince is ready to claim one—or both—of the thrones that should rightfully be his.
When Urian discovers Kyla, unaware of her ancestry, he finally has the ally—or general—he’s needed. . . whether or not she agrees.
Far from the world of the fey, Kyla has spent her life aware that her bloodlines aren’t as mortal as those around her. When one of the creatures she’s been told to hide from discovers her in the desert, she decides to protect her human family by finding her place in the world of the faeries. She can’t trust Uri, but she feels drawn to him in a way she never imagined.
Secrets are revealed. Peace is threatened. And neither family ties nor accidental love can keep the balance between the courts now.