Death's Heretic by James Sutter

Death's Heretic as a novel, would make a great Gumshoe adopted Lorefinder Adventure. It's a tale about a man who comes from a nation of atheists that serves the god of death.

Note that here, the setting is using this country of atheists not as not believing in deities. They know that these entities exist. They know that the outer planes are real. They know that they have souls. However, they do not believe in giving themselves over in worship or accepting that aid in return.

That's just a touch of background on the main character. Before I move onto some of the other elements, I'm going to put the big flashing warning notice on. If you wish to avoid spoilers, read no further.

The main thrust of the book is Salim Ghadafar's quest to discover what happened to a missing soul. There are several red herrings and much exploration of the planes in the setting. There are several characters that come under investigation that interplay with Salim.

In looking at a more investigative style adventure, it's important to have a wide selection of non-player characters in your library. By having these NPCs build up before hand, you can use them as a buffer in terms not only of time, but in setting up future adventure seeds. These individuals may be offended by the manner in which they are questioned. They may see the players as potential future allies, henchemen or catspawns to be used at a later date. By providing some interesting encounters for the characters to navigate through that don't necessarily rely on combat, the Dungeon Master is setting the stage for future use if he ever needs it.

In terms of exploration,most fantasy game settings have some type of belief system that physically exist. There is often a real heaven and a real hell. These places might be able to provide a quick shot of exploration and investigation. It allows the Dungeon Master to showcase some of the unique beings and inhabitants of the setting. In this case, Salim's quest takes him to a Limbo state where he meets the pure chaotic inhabitants that run that particular aslyum. This is in addition to his association with a Marut, an agent of law, and his middle man, the black angel on the cover. These elements bring the setting to light.

One of the better written books in the Pathfinder series, Death's Heretic manages to be done in one and provides some interesting ideas for how a soul could be yanked in the first place and how someone would go about finding it again.