Devour Me by Emily Rath — book slip

Dáinn the Devourer, a wraith bound to a dark witch, is sent to devour the soul of a rival witch, Jasper Prescott, on Burr Island. However, his mission is interrupted by Birdie Rhodes, a human who inexplicably stops him in his tracks. As Dáinn becomes entangled with Birdie, he finds himself drawn into a complex relationship with both her and Jasper. Together, they navigate a world of dark magic and dangerous alliances, where their growing bond could lead to their undoing.

First in the Devour Me Series.