de Camp and Pratt's "The Roaring Trumpet"
To be honest, I've stayed clear of The Mathematics of Magic series, of which "The Roaring Trumpet" is the first novella. I'd heard them described as "comedic" fantasy. Having recently completed my first read of "The Roaring Trumpet" that was clearly a mistake. It was an amusing tale with some things to smile about, but much in the sense that your typical D&D session often develops its own sense of humor and jokes.
With that in mind let us investigate "The Roaring Trumpet". I'll stay clear of spoilers but I will of course have to discuss the story in broad strokes. This tale was first published in the May 1940 issue of Unknown magazine. Our hero is Harold Shea, psychologist. Harold wants adventure - he takes up fencing, riding, etc.
As our tale begins Harold works at a hospital is in a conversation with his boss, Reed Chalmers. Dr. Chalmers theorizes the reason for some of his patients' problems is that their brains aren't aligned for this universe. Through use of symbolic logic it should be possible to realign their brains and in so doing project them into the correct universe from them. During this conversation they discuss possible laws of magic in another world, where magic could work because everyone would believe it would, albeit with certain rules.
Harold decides this is the opportunity to the adventure he seeks. He decides to visit a world of Irish myth and develops the formula for that universe, gathering all the gear he would need for such a trip. He then goes through the logic he has developed and, in so doing, crosses universes.
However, it seems poor Harold has made an error in his calculations and he arrives not in the universe of Irish myth but rather that of Norse myth. He encounters the likes of Odin, Loki, Thor, Heimdall, and other Norse gods and discovers the giants are up to no good, having stolen the weapons of Thor and Frey in preparation for Ragnarök.
That's the extent of the plot I will detail, suffice to say Harold goes adventuring with the gods in search of Thor's hammer. There are indeed some humorous moments in this tale. For example while at a hall he asks for vegetables, earning the name Turnip Harald.
In his adventures Harold discovers that the laws of physics and magic are indeed those of this realm and not his own - high-tech items from his (and our) no longer work for him. This also serves to explain why it is he's able to communicate with the natives of this realm, as even he himself has been changed to belong to this word. Reading these sections gave me a glimpse into what Gygax and other early authors of extraplanar adventures had in mind.
I also encountered some additional some concepts which found their way into D&D. Being a tale of Norse mythology it was no surprise to find hill, frost, and fire giants and to see the clear inspiration they served for D&D. One surprise I did have is when Harold receives a scroll which allows him to cast a spell - I'd not anticipated I'd encounter the origin of D&D's spell scrolls. There was also an encounter with a dragon who came accompanied by a strong chlorine smell.
Beyond learning about an additional inspiration for the D&D game "The Roaring Trumpet" most definitely served as an enjoyable story in its own right. The characteristics of the Norse gods and giants made for enjoyable reading as did the adventure they go on. As someone who once had a dog named Loki (who managed to get playtester credit along with the rest of our group in Decipher's Star Trek RPG) it was nice to see a non-villainous portrayal of Loki.
The Mathematics of Magic. Unless my search skills have failed me it is unfortunately only available in physical format (i.e. no e-book format, at least in the United States).