Insquidious Devotion by K.L. Hiers

Between raising a tiny demigoddess and their private investigation business, Sloane Beaumont and his husband, Loch, have their hands and tentacles full. Unfortunately, they still have to save the world—again.
Sloane and Loch are on their way to a mysterious crime scene when an old god named Cleus attacks. It’s the latest in a long list of potentially apocalyptic crises, and that’s not a coincidence. While some people just want to watch the world burn, local cultists are determined to strike the match. If their plan to awaken an evil god succeeds, they’ll get their wish.
With victims magically drowning left and right and the revelation that the old gods are real leading the public into mass panic, Sloane and Loch must gather their friends and family—and a shady local gangster—to solve the mystery and defeat new dangers. But the biggest threat may be one they never saw coming….