Gay with Me by Patricia Logan

ATF special agent Kane Delancey has a new boyfriend. After nearly losing Luca to a monster, he knows how precious life can be. He was repentant when he returned to fall on his sword with Luca but as things have turned out, it was probably the most intelligent thing he’s ever done. If he thought life was full before meeting the handsome young jeweler, he’d been fooling himself. Luca is sweet, kind, and the funniest person Kane has ever met.
Luca never expected to see Kane again but after a season of losses, the two men reconnect to find that they need each other now, more than ever. It seems that Kane no longer has reservations about the two of them and Luca can’t be happier about it. How the straight-acting Fed and the young club kid are going to blend their very different lives is a question they’ll be grappling with in the coming months. Seeing the hopeful look on Luca’s face when they discuss the problem, only helps Kane realize that there is no real choice at all.
With a serial killer targeting young men on a WITSEC hitlist with bombs, Kane and the rest of his team at the LAPD, ATF, and FBI scramble to find the man and arrest him before one more person dies. The fact that Luca was nearly a victim the last time, scares Kane to death.