Butcher & Blackbird (The Ruinous Love Trilogy) by Brynne Weaver

When two rival serial killers, Sloane and Rowan, cross paths, an unlikely friendship sparks through a twisted annual game: hunting down the world's worst, unpunished criminals. But as their darkly hilarious partnership deepens into a fierce bond, the line between bloody retribution and undeniable romance begins to blur. Packed with macabre wit, high-stakes thrillers, and a sizzling slow-burn dynamic, Butcher & Blackbird is a deliciously dark romantic comedy that proves love can bloom in the most unexpected—and gruesome—places.