The Eragon books offer the enchantment of an alternative world fully entered. Illustration by R. Kikuo Johnson

At Oxford in the nineteen-forties, Professor John Ronald Reuel Tolkien was generally considered the most boring lecturer around, teaching the most boring subject known to man, Anglo-Saxon philology and literature, in the most boring way imaginable. “Incoherent and often inaudible” was Kingsley Amis’s verdict on his teacher. Tolkien, he reported, would write long lists of words on the blackboard, obscuring them with his body as he droned on, then would absent-mindedly erase them without turning around. “I can just about stand learning the filthy lingo it’s written in,” Philip Larkin, another Tolkien student, complained about the old man’s lectures on “Beowulf.” “What gets me down is being expected to admire the bloody stuff.”

It is still one of the finest jests of the modern muses that this fogged-in English don was going home nights to work on perhaps the most popular adventure story ever written, thereby inventing one of the most successful commercial formulas that publishing possesses, and establishing the foundation of the modern fantasy industry. Beginning with Terry Brooks’s mid-seventies “The Sword of Shannara”—which is almost a straight retelling, with the objects altered—fantasy fiction, of the sword-and-sorcery kind, has been an annex of Tolkien’s imagination. A vaguely medieval world populated by dwarfs, elves, trolls; an evil lord out to enslave the good creatures; and, almost always, a weird magic thing that will let him do it, if the hero doesn’t find or destroy it first—that is the Tolkien formula. Each element certainly has an earlier template and a source, but they enter the bookstore, and the best-seller list, through Tolkien’s peculiar treatment of them. Of all the unexpected things in contemporary literature, this is among the oddest: that kids have an inordinate appetite for very long, very tricky, very strange books about places that don’t exist, fights that never happened, all set against the sort of medieval background that Mark Twain thought he had discredited with “A Connecticut Yankee in King Arthur’s Court.”

What did Tolkien do to this stale stuff to make it so potent? Another British don, Christopher Ricks, once dismissed Tolkien as “our Ossian,” referring to a third-century Irish bard, supposed to be the author of “Fingal” and other Gaelic epics, and wildly popular in the eighteenth century, whose works were actually written by his supposed “translator,” James Macpherson. Dr. Johnson knew it was a fraud, and when asked if any modern man could possibly have written such poetry replied, “Many men, many women, and many children.” Ricks meant the comparison to Ossian as a putdown—that there is something fraudulent and faddish about Tolkien’s ginned-up medievalism.

But the remark helps bring out Tolkien’s real achievement. When you actually read the Ossian epics, you find that they are shaped entirely to neoclassical tastes. The work is heavily Homeric, remote and noble, full of gloomy gray seas and doomy gray mountains, and ribboned with bardlike epithets. “The Lord of the Rings,” by contrast, begins in lovable local detail, birthday parties and fireworks and family squabbles. Tolkien’s early works—“The Silmarillion” and “The Children of Húrin,” published only after his death—are devoid of Hobbits and humors and pipe-smoking wizards; they really are like Ossian, and as dull as dishwater in consequence. Even if, as Johnson thought, a child could have written Ossian, children were never meant to read it. There’s no bright foreground to the story.

This is surely the most significant of the elements that Tolkien brought to fantasy. It’s true that his fantasies are uniquely “thought through”: every creature has its own origin story, script, or grammar; nothing is gratuitous. But even more compelling was his arranged marriage between the Elder Edda and “The Wind in the Willows”—big Icelandic romance and small-scale, cozy English children’s book. The story told by “The Lord of the Rings” is essentially what would happen if Mole and Ratty got drafted into the Nibelungenlied. (J. K. Rowling intuitively followed this part of the formula by mixing a very old-fashioned kind of English public-school story in with Tolkien’s sword-and-sorcery realm.)

Modernist ambiguity, or realist emotional ambivalence, is unknown to Tolkien—the good people are very good, the bad people very bad, and though occasionally a character may be tossed between good and evil, like Gollum, it is self-interest, rather than conscience, that makes him tip back and forth. Betrayal and temptation happen; inner doubts do not. Gandalf and Aragorn never say, as even the most patriotic real-world general might, “I don’t know which side I should be on, or, indeed, if any side is worth taking.” Nor does any Mordor general stop to reflect, as even many German officers did, on the tension between duty and morality: there are no Hectors, bad guys we come to admire, or Agamemnons, good guys we come to deplore. (Comic-book moralities, despite their reputation, are craftier; the “X-Men” series is powerful partly because it’s clear that, if you and I were mutants, we would quite possibly side with the evil Magneto.)

What substitutes for psychology in Tolkien and his followers, and keeps the stories from seeming barrenly external, is what preceded psychology in epic literature: an overwhelming sense of history and, with it, a sense of loss. The constant evocation of lost or fading glory—Númenor has fallen, the elves are leaving Middle-earth—does the emotional work that mixed-up minds do in realist fiction. We know that Westernesse is lost even before we know what the hell Westernesse was, and our feeling for its loss lends dimension to those who have lost it. (There is also, in Tolkien, the complete elimination of lust as a normal motive in daily life. The wicked Wormtongue lusts for Éowyn at the court of Rohan, but this is thought to be very creepy.)

To see the road not taken, one need only think of that parallel fantasy masterpiece, written in exactly the same decades, and on a similar scale, by a similarly eccentric Englishman: T. H. White’s four-volume retelling of the story of King Arthur and his court, “The Once and Future King.” White, too, modernizes and sweetens his epic story, but he more overtly moralizes it, and he makes it emotionally ambiguous as well: What is right? Who gets to decide? Does duty come before passion? White worries about ambiguity and halftones: the impotence of the idealist King; the beauty and doom of the adulterous lovers; the capacity of good law to make bad judgments—it is Arthur, not Mordred, who has to sentence Guenevere to death. Where White’s literary task was to study the fate of epic ideals in a recognizably real world, Tolkien’s was to find a way to create the illusion of the real world in an idealized epic one. But though “The Once and Future King” inspired the musical “Camelot,” our new Arthurian romances are likely to be given a Tolkienesque treatment, focussing on clashes between armies, not within souls.

If Tolkien was, as Ricks insists, in any sense our Ossian, then perhaps Christopher Paolini is our Chatterton—the early Romantics’ “marvellous boy,” who, inspired by Ossian, made up his own set of pseudo-medieval poems, attributing them to a poet named Rowley, and claiming that his father found them in a chest. One difference is that Chatterton paid for his poetry with his life, while Paolini gets paid for life. Paolini was only eighteen when the first volume of his Eragon series, the tale of the dragon rider Eragon, was privately published, in 2001. The book and its sequels were quickly taken up by a mainstream publisher, and the series is now a genuine sensation. The final installment, out just a few weeks, has had a first printing of more than two million copies.