"Badlands (Cassie Dewell, #2)" by C.J. Box

This is a modern western, fast moving with well defined characters. It has the background of cold whether in a North Dakota boom town rampant with drugs. Suspense builds at a good pace throughout the book and I had trouble putting it down. 
Cassie Dewell is a determined police woman who wants results even to the point of breaking the law. It wouldn't take much for her to slip to the dark side to get her desired results. She doesn't realize that she may have a kindred soul in her new superior. He knows her background and she may be just the kind of investigator he is looking for. 
Although in another state, she has not given up on the capture of The Lizard king, setting a trap in her spare time.