Grim Shadows by Jenn Bennet
I have to admit that at first I was a bit annoyed with the male lead, Lowe Magnusson. When he first meets Hadley Bacall, he just keeps going on and on about her rear-end. Thankfully he eventually moved on to noticing her as a person. And they are a good match.
Lowe is a con-artist, liar and a thief, but he has a truly good heart. Who doesn't love that type of bad boy, the kind that's just bad enough to be interesting but isn't going to intentionally hurt the people he cares about? Hadley has spent her life proving she's worthy and trying to keep her spirits at bay. Because they do want to kill someone, they're just waiting for her to get angry enough to let them. And she comes close - Lowe is quite good at pushing people's buttons.
While this is a romance, Lowe and Hadley are also on a mission. They need to collect the pieces of an artifact, but...