Showing No Mercy by Sherrilyn Kenyon

Shapeshifter Dev Peltier thought he knew it all. But one night when a Dark-Hunter, who is also an official member of the Dogs of War, sashays into his bar, he realises that he might have met his match.

Samia, aka Sam, was one the fiercest Amazon warriors in her tribe. But an act of brutal betrayal made her a Dark-Hunter and she's been angry ever since. Live fast, fight hard and enjoy the night. That's her credo. But as old enemies and new move into New Orleans, she realises that Dev just might be the only hope she and mankind have to save the world.