The Devil's Detective by Simon Kurt Unsworth focuses on Hell's Information Man (one of 3 at the outset), Thomas Fool. Fool's role in the afterlife is investigating crimes and passing the results up to the bureaucracy. He's also a lackey for said bureaucracy, thus why we meet him at the entrance to the tunnel to Heaven awaiting the Angelic delegation to arrive for negotiations with Fool's boss, Elderflower.
Said emissaries find out quickly that while in Hell, they must follow Hell's rules. Adam, of Gabriel's line is the nice one, while Balthezar is of Michael's lineage, and tends to think the current Hell of bureaucracy and random torment doesn't include enough suffering for the sinners within.
In this iteration of Hell, Souls swim in the ocean of Limbo, get fished out with no knowledge of who they were in life or why they're in Hell, only what role they are to perform in Hell until they either die again (and have to repeat the process) or they get elevated. Thus one of the major punishments is that of Hope. Hope of atoning enough to ascend, hope of surviving another day. (This differs from Dante's conception, where there was no hope in Hell. for that, one had to suffer
Not long after meeting, Balthezar gives Fool one of his feathers, kind of as a joke. Mind you, everyone in Hell covets the damn thing, including the Man of Plants and Vines. Said man is somewhat like the sentient Vines in The Ruins, except he still has sort of a physical body. The Man trades in information and favors.
The major thrust of the novel, though, is the dead Genevieves, male prostitutes who whore themselves out to demons. The few witnesses (who don't really see much of anything) report nothing but a blue flash upon death. Those that Question the dead find that the bodies have no souls, leading to the conclusion that something is eating the souls, rather than sending them back to Limbo.
Fool, who spends most of the novel trying to avoid being noticed, gains notoriety among both demons and humans as he investigates, and by the end, we do indeed know whodunit and why.
While there are more than a few red herrings thrown in, it's not that hard to spot at least one part of the final twist fairly early on. Not a bad read, but not anything I see myself picking up again.