Fallen Angel by Tamsin Baker

If LA had the gall to spin the lie and call themselves the “city of Angels,” maybe New York should grab the title “city of Demons” and be more upfront about it.
Defeating the forces of Hell won’t be easy, even for Heaven’s most fierce protector.
Gabriel is forsaken. His sins against Heaven have earned him a place on Earth among the tortured ones. There’s only one way to reclaim his place among the Angels; He must save the souls of the damned.
But when he meets Kadie, a young, beautiful woman who he must protect against the forces of evil, his entire existence is thrown into question. She isn’t the run-of-the-mill human girl—she’s a powerful Witch, and might have what it takes to save the world from the powers of darkness.
Can Gabriel overcome the shame of his fall from grace, and rise to become the hero Kadie, their miracle baby, and the entire world needs?