This will likely be one of the most disjointed, rambling, incoherent and (most likely) useless and unnecessary posts that I have made in my years posting about Middle-earth, etc. And yet I feel compelled to try to express this thought, unoriginal and perhaps even uninspired as it is.
I am struck by the serendipitous nature of how Tolkien's universe has continuously been expanding in how it has been exposed to the public. It has followed no one's plan, not Tolkien's himself, not his son Christopher's, certainly not Peter Jackson's or that of the various other artistic and commercial individuals that have been involved in this process, though all of them had some influence. I would tempted to argue, nonetheless, that it has followed some plan beyond the ken of all of them.
The first real exposure to Tolkien's universe (my apologies to Tom for not including the previous appearance of Bombadil) came more or less accidentally with the publication of the mostly unrelated children's book, The Hobbit. The framework of the mythology underpinning the universe already existed at this time, of course, but only inserted itself into that story in the most superficial of ways.
The unexpected success of The Hobbit caused Tolkien to be distracted from turning back to the legends of the Elder Days, because of the desire of his publisher for a sequel to The Hobbit. It is well documented, of course, how that sequel became subsumed by those old legends, so that the result, The Lord of the Rings, became instead a continuation and conclusion of those old legends. Yet despite Tolkien's desperate desire to have the full set of legends, from the creation myth of the Ainulindalë through the Wars of the Jewels and of the Ring, published together as one complete saga, circumstances (including Tolkien's own stubbornness) contributed to cause only the latter part of the tale, "the account, as it were, of its end and passing away before its beginning and middle had been told" (as Tolkien puts it in the Foreword to The Lord of the Rings) to be published.
And, of course, The Lord of the Rings became remarkably successful, far more then The Hobbit, and far beyond Tolkien's or anyone else's wildest imagination. And a large part of that success was due to the sense that that work gives to being a reflection of a universe of great depth. It is the "many glimpses of the yet more ancient history that preceded it" (to again quote from the Foreword) that gives it that sense of depth, and yet great mystery. I am certainly not the first person to assert that The Lord of the Rings would not have been nearly so successful (and perhaps not successful at all) if it had in fact been published as Tolkien had wished as part of the the greater history of his created universe.
But, of course, the great success of The Lord of the Rings opened up a market for the publication of the older legends (older both in terms of the time period they described, and in terms of when they were begun by Tolkien). But then it was that stubbornness of Tolkien's, combined with the very complexity of his unique way of creating, that conspired to continued to keep the older legends out of the public eye. Tolkien kept expanding his creation, and changing it, and adding different versions of the same tales, and he was never able to publish anything of the older legends during the period of the rest of his long life.
And there it would have likely stood, with his legacy largely standing on the success of The Lord of the Rings (and to some extent The Hobbit), but the bulk of the true nature of the universe that he created being largely unknown. Except for the curious nature of his youngest son, Christopher. Christopher long shared a great interest in his father's work, from the days of The Hobbit when as a child he was largely the intended audience, through the creation of The Lord of the Rings, a large portion of which was sent off to him in letters as he fought in World War II. He shared his father's love of language, and followed in his footsteps as Professor at Oxford. He was, therefore, well situated to act as his father's literary executor. After his father's death, he set out (with the help of Guy Kay) on the "difficult and doubtful task of preparing the text" of The Silmarillion for publication. And for the first time, much of that deeper world that is glimpsed in The Lord of the Rings is revealed, including the creation of the universe, it's cosmological structure, and the desperate history of the first born of the fathers of Men that fought by their sides in their hopeless wars against the original dark lord, of whom Sauron was but a servant.
Yet many people felt a certain disappointment with The Silmarillion. For all of its history and grandeur, it lacked the narrative depth that made The Lord of the Rings so compelling. Little did anyone know at that time, however, what a condensed and amalgamated version of the old legends the published Silmarillion was. We gladly accepted it as the "authorized version" but we hungered for more. That hunger was partly satisfied with the release of Unfinished Tales, which gave some snippets of the kind of narrative depth that we loved in The Lord of the Rings. But only snippets.
Then Christopher made the critical decision to publish the oldest versions of the old legends, The Book of Lost Tales, and the Lays of Beleriand. That led naturally into the huge labour of full History of Middle-earth series. With the completion of that task (which I fully believe no one but Christopher Tolkien could have accomplished) the full depth of Tolkien's creation became available, for those willing to wade through the huge patchwork of material revealed. Not only was most of the various versions of The Silmarillion tale now available in their fuller depth, these legends were tremendously supplemented by the deep philosophical musings of such works as the Athrabeth Finrod Ah Andreth (and particularly its commentaries), The Laws and Customs of the Eldar, and The Shibboleth of Fëanor.
With the completion of the History of Middle-earth series (and with the upcoming publication of the Children of Húrin), a full appreciation of Tolkien's universe is possible. Fuller, I would argue, then would have been possible if Tolkien had succeeded in publishing the Saga of the Jewels and the Ring as one work, as he had originally wished. I am tempted to say Tolkien was meant to publish only the The Hobbit and The Lord of the Rings in his lifetime, and that then Christopher Tolkien was meant to publish first the condensed and somewhat unsatisfactory Silmarillion, followed by Unfinished Tales, then The Book of Lost Tales, The Lays of Beleriand, the rest of The History of Middle-earth, and The Children of Húrin. And that is, perhaps, an encouraging thought.
And, of course, the tale does not end their. These works have been supplemented by a remarkable body of interpretive works, led by such brilliant scholars of Tolkien's work as Tom Shippey and Verlyn Flieger (dare I hope that my own small work will eventually add to that glorious tradition?). And the universe that Tolkien created was further expanded in the world of cinema, first in a small way with Bakshi and Rankin/Bass' animated efforts, but then on a huge scale with Peter Jackson's wildly successful films. Whatever one thinks of those films (and I hope that whatever discussion this post generates, if any, does not turn to the comparative merits of the films) it cannot be doubted that they have greatly expanded the public's perception of Middle-earth. The lavish LOTR musical also contributes to that expansion, to some extent.
Finally, it is in the gaming world that this process seems to be taking the most revolutionary turn. Middle-earth games have existed for many years, but the new LOTR Online game is taking the process to new heights, allowing individuals to completely immersed themselves in Tolkien's Middle-earth. I myself am not a gamer, and with my 20th century dial-up internet connection, I'm not likely to participate in this latest development. But that does not stop me from appreciation the latest step in Tolkien's Expanding Universe.
Believe it if you need it,
if you don't just pass it on.