Bloody Vows by Lisa Renee Jones

FBI agent Lilah Love leads a complicated life. She’s engaged to Kane Mendez, a man most call dangerous, but hey birds of a feather, do flock together. She’s dangerous, too, and in ways only Kane understands. As for their happily ever after, well that might have to wait. Right now, an old enemy who should be dead is still living, Junior, her mystery letter writer, is stirring up trouble, and her family is trying to prove they’re crazier than her. On top of that she has a new case: a dead woman in a bloody wedding dress. And since Lilah knows all too well there is no such thing as coincidence, clearly someone is sending her yet another message.