In Savannah Reid series, main character is close friends with a gay couple Nava, Michael. Mystery series featuring detective Lauren Laurano. The Dog Collar Mystery. Trouble in Transylvania. Zubro, Mark Richard.
Protagonist is a spy and gay.
Takes place during WW2. I thought the author did a great job with all the double life stuff. Ethan of Athos. An entire planet of men being visited by a woman. G.K. Hall, 1990.