Once You're Mine (Possessing Her #1) by Morgan Bridges

"The Tormentor: Calista belongs to me... she just doesn't know it. The first time we met, I wanted her. The next time, I was obsessed. I watched her. I followed her. It only deepened my need to possess her. Once she's mine, I'm never letting her go. The Target: Hayden Bennett is a monster, in and out of the courtroom. Unfortunately, I need his help. What was supposed to be a simple transaction turns into something else. Something intense. He's always there when I need him, but I don't know if trusting him is a good idea... Once You're Mine is Book 1 in the Possessing Her Duet that ends on a cliffhanger. It contains a morally gray hero that's OTT/JP, a stalker who falls first, has Touch Her & Die energy, and is willing to do whatever it takes to have her. (A complete list of the TWs can be found on the author's website)."