For more than three years, I've been writing and re-writing my novel involving immortal characters.
Now I'm finally gathering courage to write a query letter and begin searching for agents. My problem is that I don't know what kind of agents to contact, as my book seems to fall somewhere in between genres.
Without actually getting into the plot, my book is an ensemble piece involving seven immortal characters, some who have lived merely decades, others centuries or millennia. The setting is contemporary (2018, mostly inside a hotel). The book borrows a lot of tropes from the mystery genre, especially from traditional mysteries (a murder in a confined space where all the characters know and suspect each other, lots of red herrings, a fair challenge to the reader where all the clues are presented throughout). The central question is not a whodunnit, however, but a whydunnit and it involves something related to the characters' condition as immortals (not the origin of immortality itself).
Here's the difficult part. These immortals are simply long-lived characters who come back to life upon death; nothing sets them apart from normal people besides their prolonged existence. They don't have any special powers. There is no magical system inside the story. There are no other paranormal beings inside the narrative (think ghosts or vampires or werewolves). Thus this can't fall into the paranormal mystery subgenre.
I've turned to fantasy too, but most subgenres that seemed somewhat plausible (contemporary fantasy or urban fantasy, for example), seemed to be quite heavy with the supernatural elements; my book isn't. If anything, it has a pretty rational approach to the issue of immortality.
Somebody in my writing club suggested magical realism. The problem is that this genre is about the complete opposite of my book in terms of tone (since it involves a certain mysticism, languid pace and flowery prose). My book is fast-paced, full of snappy dialogues and does actually treat immortality as something special, rather than a natural occurrence.
I'm afraid if I pitch my book as just a mystery, most agents/publishers/mystery readers will be turned off by the supernatural element. If I pitch this as fantasy or paranormal mystery, they will be expecting magic and paranormal beings. I don't know enough about SF subgenres to see if there's anything that fits, as I've only read a bunch of classic SF novels. Thus, I can't seem to figure out my audience either.
Thoughts? Also, are there any other books that fall between similar genres that you could tell me about (mystery with a slight supernatural twist)? It might help me tremendously, as I'd have a starting point in seeing what kind of audience these books attracted.
Edit: My book is somewhat similar to Death Note in that the supernatural element is more of a plot device/means for the mystery to happen, not the mystery investigated itself. If you suspend your disbelief and accept that Shinigami/Death Notes (or in my case, immortality) exist, then the mystery itself focuses on a (series of) murder(s), involving humans and caused by humans. That's one of the extra reasons why I hesitate to call this fantasy.