There are more amusing faux book covers here, one of my favorite being:
Shocked though I'm sure you all are, I don't have much liking for Marion Zimmer Bradley's re-telling of the Matter of Britain. But that's not what I want to talk about in this post. Instead, I'm going to put forward a position that I hope will make clear my own perspective on the role of "tradition" in D&D.
The legend of King Arthur is, to put it bluntly, a mess. They're a mass of conflicting tales from a variety of different sources that have, over the years and largely through the overwhelming influence of Thomas Malory's Le Morte d'Arthur, acquired a kind of incoherent coherence. That is, though there are many strands, both cultural and literary, within the legend of King Arthur, those strands have nevertheless coalesced around some central themes, events, and characterizations in a way that makes it possible to say with some degree of certainty that the legend of King Arthur is about certain things, includes certain events, and has a cast of characters with recognizable personalities and features. In short, despite its origins, it's not at all unreasonable to talk about "the legend of King Arthur" and expect that most educated people in the Western world will know the rough outlines of what you mean by it.
One of the many reasons why the legend of King Arthur can be told and retold again and again is that, aside from its timeless themes, it contains so many cultural and literary strands within it that any given storyteller can choose to emphasize this one over that one in order to keep the legend "fresh" and engaging to a variety of audiences. Not all of these new takes on the legend work, of course, but that's not because of the weakness of the source material. In my opinion, it's because the only way to retell the legend of King Arthur is to do so in ways that are consonant with its thematic core. Betray that core and what you're left with isn't a retelling of an immortal tale but the creation of a merely derivative one.
I recall reading somewhere that Professor Tolkien hoped that, one day, Middle-earth might become the focus of its own legend cycle, with other storytellers picking up what he had done and using it to create additional tales so as to establish a proper English mythology (Tolkien famously deemed King Arthur unsuitable both because of its Continental, specifically French, influences and the way it mixes magic and Christianity). H.P. Lovecraft's Cthulhu Mythos already is something similar: his alien gods and blasphemous books are commonplace in contemporary fantasy and horror. I've often felt that both Star Wars and Star Trek work better when viewed as myth cycles, with each new series, movie, or book viewed as a retelling of the same basic story rather than as an addition to the overall story. Indeed, unless I am mistaken, Star Trek novels have no continuity between them, except whatever their authors might choose to accept, thereby freeing each author to use as much or as little of the "myth cycle" as suits their dramatic purposes.
A myth cycle isn't a "story" precisely, though it may include many very specific events within it. The legend of Arthur, for example, includes a number of events common to most of its tellings. However, the myth cycle can't be reduced to a series of events or even a collection of characters, because all of these can be altered or outright ommitted, especially if the myth cycle is large and convoluted enough. So, a myth cycle's foundation is its thematic core -- what it's about; that's its "story." The truth of this is pretty plain when you look at, for example, many putative stories of the Cthulhu Mythos. The work of August Derleth contains innumerable references to the gods, monsters, tomes, and characters of HPL's work, but its themes are so different and, in many ways, contrary to those of his predecessor that I don't think they can reasonably be deemed "Cthulhu Mythos stories" except in the most analogical sense.
The key, of course, is locating the thematic core of a myth cycle. Once you've done that, it's possible to recognize the derivative works for what they are. I realize, of course, that my position will be controversial, since it explicitly excludes revisionism from being part of the myth cycle. I don't think this is an unreasonable position, but I know that not everyone will accept it. Nevertheless, the point remains that myth cycles have a coherence to them that transcends the welter of specific things associated with the myth cycle. That's why you can tell a perfectly good Arthurian story in which certain characters or events never appear. It's also the reason why most of us, if reading a story that purports to be part of the myth cycle, can intuit whether it really belongs to it or not. I contend we all have a sense of the thematic core of most myth cycles with which we're quite familiar and can thus tell whether the author is working within the tradition or not.
D&D, being a game rather than a series of tales, can't really be viewed as a myth cycle in quite the same way. Certainly, there's the Gygaxian Canon, but I long ago came to the conclusion that it's a mistake to conflate D&D with the Gygaxian Canon. I find most of the wailing and gnashing of teeth -- "Save the Great Wheel!" and all that -- about the changes to the Canon in the new edition to be missing the forest for the trees. Despite this, I think there is a central "story" to D&D, which is to say a thematic core, and it's from this core that all things that wish to call themselves "Dungeons & Dragons" must draw. What is that thematic core? I hope I can be forgiven for saving my answer to that question for a later post, but, rest assured, I'll be discussing it at some length over the next day or two.