Shadow Crusade (Shadowthorn Book 1)

Beware the Shadowthorn. Dark. Desolate. And crawling with demons. But Halira Devonshire isn't afraid. As a demon huntress, she's vowed to eradicate demon-kind. Until she learns that the lines between human and demon are blurred, and Halira finds herself falling for a roguish demon-man intent on unraveling her world.