The Demon King by Heather Killough-Walden

Dahlia Kellen has been through hell. Raised in a fae society that slowly drove her mad, she turned traitor against her people and was cast out. But in an act of heroism that clearly exposed her for the good she was, she rose up against the true evil threatening her people, and in her efforts to stop that evil, she was terribly transformed. Now dark, different, and feeling truly exiled in her soul, Dahlia has a chance encounter with a man in Boston. A man whose gaze is as dark and haunted as her own… and whose craven desire for her and dangerous, powerful bloodline will show Dahlia that for her, hell is just the beginning.

“I’ve come with a message about your father,” said the stranger.
“You’re speaking of Marius.” Marius was dead. Laz would know; he’d killed him.
But the messenger smiled. “No, no. Not quite,” he said, white teeth gleaming in an unholy grin. “Think bigger. Think badder.”

Steven Lazarus is a seasoned detective with the Boston police force who has always served and protected, and done so by the book. But the Akyri King’s insides are heating up, a painful yearning is tearing away at him, and his tall, strong body has become capable of a dark, violent magic he can barely control. His dangerous past has caught up with him, and he can scarcely stand to look at his own reflection. He doesn’t recognize the man staring back at him, and that terrifies him.

Because he knows the powerful, hungry man in the mirror wants Dahlia Kellen just as badly as he does. And if he has to, he’ll raise hell to claim her.

The Demon King is the 9th book in the best selling The Big Bad Wolf spinoff series, The Kings, by New York Times and USA Today bestselling author, Heather Killough-Walden.