His Dark Reflection (Heart and Haven #3)
Heloise West

Homicide Detective Hank Axelrod is good at digging out secrets, maybe because he hides a big one of his own. He also suspects his husband has one foot out of the door of their marriage and the specter of single life looms unpleasantly on the horizon.
A murder resembling a previous one brings Nick into his world, a man who claims to be a mystery writer looking for a real-life resource. Hank’s instincts say he’s more than that, and he’s rarely wrong.
Torn between the errant soon-to-be-ex husband and the distracting, sexy stranger, Hank needs to focus all his attention on his murder case before he becomes the next victim.