Why is Tolkien's Middle-earth so popular?

The Telegraph recently republished what the editors call an interview with Professor J.R.R. Tolkien first published 22 March 1968. Though it reads more like a news story than an interview, the piece makes for fascinating reading not only because of what Tolkien himself says in it, but because of the way in which the interviewer describes the professor and his literary work. Among the many things we learn is that Elvish should be sung "like Gregorian chants."

Consider, as just one example among many reasons why you should read this interview, this description of Tolkien:

Tolkien, who describes himself as "tubby", has grey eyes, firm tanned skin, silvery hair and quick decisive speech. He might have been, 50 year ago, the model of the kindly country squire. Any hobbit would trust this man, any dragon would quail before him, any elf name him friend. Effortlessly, he compels you to admire him as much as  – and herein lies his charm  – he clearly admires himself.

To the small but bitter anti-Ring coterie – some of whom profess to see sinister meanings in the text – his very ebullience would presumably constitute an irritant. But to devotees, all this adds up to the perfect cult-hero.

Though I was, of course, never able to meet Tolkien (he died five years before I was born), I certainly count him among my heroes, both because of the brilliance of his legendarium and because of the exemplary character we find in his letters. I hope someday that it might also be said of me that "any hobbit would trust this man, any dragon would quail before him, any elf name him friend." Not bad praise, that.

In a passing description of The Lord of the Rings, the interviewer seems to implicitly ask why Tolkien's great work is so popular, both among academics and non-academics alike:

Despite the fact that his books lack perversion, four-letter words, homosexuality and sadism – virtually everything that makes 20th-century fiction so commercially desirable – the Professor and those connected with his publications have found the streets of Middle-earth paved with gold.

Curiously, the interviewer doesn't delve into this any deeper than to say that Tolkien "never expected a money success" from the book, which begs the question as to why his works were and remain so popular. The answer is very simple and cuts straight to the heart of his life's work:

But I should say, if asked, the tale is not really about Power and Dominion: that only sets the wheels going; it is about Death and the desire for deathlessness. Which is hardly more than to say it is a tale written by a Man (Letter to Herbert Schiro, 17 November 1957)!

A few months later, Tolkien briefly explained what he meant by this desire for deathlessness:

Though it is only in reading the work myself (with criticisms in mind) that I became aware of the dominance of the theme of Death. (Not that there is any original 'message' in that: most of human art & thought is similarly preoccupied.) But certainly Death is not the Enemy! I said, or meant to say, that the 'message' was the hideous peril of confusing true 'immortality' with limitless serial longevity. Freedom from Time, and clinging to Time. The confusion is the work of the Enemy, and one of the chief causes of human disaster. Compare the death of Aragorn with a Ringwraith. The Elves call 'death' the Gift of God (to Men). Their temptation is different: towards a faineant melancholy, burdened with memory, leading to an attempt to halt time (Letter to C. Ouboter, 10 April 1958).

Everything that makes Tolkien's work so beloved to his fans and readers - friendship, fidelity, courage, charity, in effect, everything of virtue and heroism - is found in his characters' desire for deathlessness, a desire which we all share, whether we recognize it or not. In his own way, Tolkien shows us this desire, warns us of its dangers, and shows us the way to its fulfillment. This is what makes his life's work so popular, in the past, today, and for years to come.