Night Sins by Lisa Renee Jones

A man of darkness, a man of passion, trapped by temptation and desire. It’s an inviting, achingly pleasurable alchemy no woman can refuse . . .

In the battle between good and evil, Kayla Ward knows vampires are strictly off limits. As a Watcher she is sworn to protect humankind from the nightwalkers. But a series of murders–the victims all women–leaves Kayla with only one choice: to join forces with the dark side. It isn’t her fault that Ethan’s seductive allure triggers every zone of pleasure in her body . . .