A Curse Like No Other. The Feral South, #1

Mercy Sinclair has nothing left to lose. A ruthless band of deserters saw to that, brutally killing her brother and destroying their homestead. However, they weren't men. They were something...otherworldly--soldiers who turned into beasts under the light of the moon. Armed only with a dead man's gun, and a thirst for revenge, she's determined to make the monsters pay--with blood.  Anson Davis has been tracking Captain West and the Dalton boys since the night they massacred his troop, killing with little remorse.
Left to die, he barely survives, only to find out he was turned into the very monsters who slaughtered his Union brothers. Fueled with a vengeance, he's nearly caught up to the trio of wolf-like men several times, but he's never gotten this close. Though arriving too late to stop another ruthless murder, Davis must decide whether to join forces with a woman, hell-bent on retaliation, or get out of her way.