When I was writing The Glass, I put in a couple of bits that were weirder than the rest of it (which is saying something) essentially because I wanted to do something with Medieval Vision Literature. I did my MA on the stuff, back before I wandered off into other branches of history for my PhD, and I felt like there would never be a better opportunity to make fun of the often very odd things the likes of Bede included in theirs.
Which is why I included things like an estate agent giving my main character a piggyback over a fiery lake, while providing him a table tennis bat in case the locals decided to lob sulphur their way. Aside from the estate agent, and the bit where it was clay jars rather than a racquet, this is almost directly from Bede's Visio Drycthelmi.
It's the sort of thing that was going to make about three people in advanced medieval studies laugh when they got it, but since I was writing what amounted to a comedy version of a lot of the paranormal/urban fantasy stuff with angels and demons in, it seemed to fit. Literary references=depth, right? Well, no, but we can pretend, while we're going through the standard parts of the genre...
And then it occurred to me that actually, your basic medieval vision of the afterlife has a fairly well defined structure too. Odd events rip someone out of their normal life (usually following an injury or illness) they meet a guide. That guide shows them a series of events/characters, while often the MC gets things wrong. Typically the MC is then left without the guide temporarily. When the MC gets them back, they're more in control of the experience, even as things often seem to spiral out of control. They have a moment of seeing things perfectly, before they're dumped back into their own life, completely changed.
Put like that, there wasn't any reason why I couldn't follow that through my novel. So this one owes a lot to medieval vision literature. Even some of the jokes.