Faerie Protective Services by Robert McKinney

An ordinary man is pulled into a hidden agency tasked with policing the messy border between humans and the fae; as he trains and works cases, he confronts dangerous supernatural predators, faerie politics, and the bureaucratic absurdities of a protective service that must keep both worlds from tearing each other apart. The story blends action, dark humor, and world-building as the protagonist learns the rules of faerie law, discovers unsettling conspiracies, and must rely on growing skills, stubbornness, and unlikely allies to survive and protect those caught between realms.