The Courtship of Julian St. Albans - Amy Crook

Alexander Benedict is a misanthropic thirtysomething magical consultant, working with the Agency's top homicide detective, and perfectly content with his life, thank you very much. Julian St. Albans is the youthful heir to his family's fortune and affianced to his beloved Cecil Mandeville, a family friend as well as Julian's lover. When Mandeville is murdered using magical means, Alex is brought in on the case. It's the worst day of Julian's life, but until they meet, it's just another case for Alex. Neither of them have any idea how their lives are about to change. Alex has to disentangle the magical threads until he can catch the murderer, and to do that he has to put himself right in the thick of things. His long-denied family connections get him invited to participate in Julian's Courtship as a Suitor, where he can observe the suspects firsthand. He just has to stay alive long enough to figure out which of the competition thinks Julian is a prize worth killing for."