He’s Mine by Claire Thompson

A new and unexpected love… An ex with revenge on his mind…
Ben’s not in any hurry to fall in love. Sure…he misses the passion and the sweet caress of someone special in his life, but after freeing himself from his last mistake of a boyfriend, it’s time to reevaluate his choices. Until a gorgeous, fascinating guy slips into the seat beside him at a mutual friend’s wedding…then all thoughts of going slow vanish.
Adrian keeps the men in his life at arm’s length…it’s safer for everyone. Casual hookups without emotional entanglements are his specialty, and the guy sitting next to him looks to be perfect for the job. But as the evening progresses, a hot, steady flame of desire flares within him, and Adrian has to tamp down the sparks. Because Ben has the potential to become something different…something more.
When old secrets are revealed, Adrian and Ben must come together to heal past wounds, and that includes dealing with a dangerous ex who won’t take no for an answer. When threats to their personal and professional lives escalate into violence, they will have no choice but to take action to protect their newfound love.