Uncanny Collateral. Valkyrie Collections, #1

Alek Fitz is a reaper, a collection agent who works for the supernatural elements of the world, tracking down debtors and solving problems for clients as diverse as the Lords of Hell, vampires, Haitian loa, and goblins. He's even worked for the Tooth Fairy on occasion. Based out of Cleveland, Ohio, Alek is the best in the game. As a literal slave to his job, he doesn't have a choice. When Death comes looking for someone to track down a thief, Alek is flung into a mess of vengeful undead, supernatural bureaucracy, and a fledgling imp war.
As the consequences of failure become dire, he has few leads, and the clock is ticking. Only with the help of his friend Maggie-an ancient djinn with a complex past-can he hope to recover the stolen property, save the world, and just maybe wring a favor out of the Great Constant himself. It's a hell of a job, but somebody's got to do it .