I had actually done a lot of personal research on Appendix N prior to this game jam for a different project, and I wanted to share some resources and knowledge in case anyone was interested in exploring the topic further.
Where did it come from and who is on the list?
The original Appendix N comes from the tail end of the Advanced D&D Dungeon Master's Guide developed by Gary Gygax. An earlier version of this list actually appeared in Dragon Magazine #4, but it was expanded by the time of the official release in the DMG into the list we refer to today. Gygax cites here and in Dragon Magazine #95 the works of Jack Vance, Robert E. Howard, L. Sprague de Camp & Fletcher Pratt, Fritz Leiber, Poul Anderson, A. Merritt, and H. P. Lovecraft as the primary fictional influences on the development of the game. He actually goes out of his way to downplay the influence of fantasy genre titans like J. R. R. Tolkien and Michael Moorcock as "minimal" despite their now historic legacy, but he does give them a nod in the original list. The underdiscussed "little brother" of the appendix (though perhaps more comprehensive) is the Inspirational Source Material list featured at the back of Tom Moldvay's Basic D&D that was first published only a few years later. If you didn't know, for a time, two versions of D&D were being simultaneously published by TSR, and these two lists have a lot of overlap.
What is the list's influence on roleplaying games and literature today?
Many people continue to reference works from the original list as part of their inspiration for fantastic game ideas, and the concept of including an appendix of influential works still endures. Appendix N was reissued as Appendix E with the release of D&D's fifth edition Player's Handbook, now updated to include seminal works of speculative fiction published since the release of AD&D, best-fit titles for authors only mentioned by name in the original list, and some of the game designers' personal picks for major influences on the game's development. Other games, like The Electrum Archive and Vaults of Vaarn, include their own unique appendices of influences like books and other media, and some games like Hyperborea and Black Sword Hack are stylized as homages to specific works and subgenres featured in Appendix N. Goodman Games, the publisher of Dungeon Crawl Classics and many old-school 5e modules, maintains an active blog talking about the writings and ideas of the list's authors. As D&D and roleplaying have become cultural titans in their own right, some authors have flipped the script and used games as inspiration for their own writings.
TTRPGs and speculative fiction are basically in constant conversation, and Appendix N is a touchstone for this exchange. For example, after playing D&D with Gygax, Andre Norton (of Appendix N fame) wrote a novel inspired by the session: Quag Keep. Decades later, this book is listed as inspirational reading in the aforementioned 5e Appendix E. Another case is the influence of Robert E. Howard's Conan stories, which not only inspired the early tone and structure of D&D, but also led to the 1980s Conan films, which in turn were adapted into official D&D adventure modules. Circle of life, baby.
Man, that's a lot of books, but I want to try reading some. Where should I start?
Start wherever you like, but I also recommend perhaps reading a short story anthology to see which authors you might like to read more from. One of the latest and greatest in my opinion is the aptly named Appendix N, Revised and Expanded Edition: Weird Tales from the Roots of Dungeons & Dragon, featuring works by authors from the original list and their contemporaries. I also personally like Weird Tales: 100 Years of Weird for its inclusion of a variety of swords-and-sorcery and horror stories from both classic and new authors. Weird Tales is a long-running pulp magazine where many of Appendix N's authors actually got their publishing start. If you wanted to look a little bit deeper into the history of the literature itself, I've heard good things about Flame and Crimson: A History of Sword-and-Sorcery. Lots of research has been done on the history of this subsection of literature and of the history of TTRPGs themselves, and a quick search yields a ton of rabbit holes, I promise.
Hopefully some of you find this topic interesting, and I hope it helps you discover something inspiring for yourself!