Hired Gun by Christine D. Shuck

Shane Ellis is a hired gun, determined to do his job, and keep his clients alive, no matter who is trying to kill them. Shane lives by and enforces The Code, a strict set of rules that have given his clients the highest survival rate – despite the dangers they have faced. Follow The Code and you stay alive. But Shane isn’t prepared for Lila, sexy, stubborn, and determined to ignore his rules. And Lila isn’t prepared for what he will do when she breaks each and every one of them.