J. R. R. Tolkien's "Unfinished Tales," edited by his son, Christopher, is an assemblage of brilliant fragments that gleam in scattered but splendid isolation. Though they want context and thus lack full luster, the tales -- perhaps because of their piecemeal nature -- are all the more intriguing. Imaginative might-have-beens, they point to the vast cosmic scheme Tolkien envisaged, one of the boldest literary enterprises of the century.

His aim was so bold, in fact, that from the start he was doomed to fail. Tolkien attempted to invent not just a limited vision of reality, a fictional postage stamp of his native soil, but a literature of an entire nation, a complete mythology with its own cyclical history, complex languages and unique creatures. It is astonishing that his Oxford don, harried by teaching duties and financial worries, succeeded in producing -- along with several scholarly editions and translations, seminal critical works and numerous short tales -- "The Hobbit," the three-volume "Lord of the Rings," and "The Silmarillion." Tolkien's intentions and efforts rank as heroic; his failures as glorious.

Nonetheless the question arises: When Tolkien has written so much so well, why should we pore over mere fragments which can only disappoint heightened expectations?

In his response to this question, Christopher Tolkien is characteristically modest and accurate. Certainly, he writes, these tales provide a plethora, a veritable dragon-horde of esoteric facts and curious details that Middle-earth specialists will treasure. The tales also, as expected, contain overlappings and correspondences with the published canon that even a casual reader of Tolkien can assimilate. Several scenes composed for inclusion with previously published material, then later excised, give a fuller picture of Tolkien's intentions. For example, additional information on the ring of power -- lost by Isildur, found and lost by Gollum, only to be retrieved by Bilbo -- is most valuable to an understanding of Tolkien's universe.

Even more intriguing, Christopher continues, and another significant reason for publishing the unfinished tales, are the numerous contradictions, matters about which Tolkien either changed his mind or remained undecided. "The History of Galadriel and Celeborn," for example, called by Christopher "a primary strand in the history of Middle-earth," often conflicts with what Tolkien wrote later. Such inconsistencies Chirstopher wisely lets stand.

Thus these stories are like individual mosaic stones not yet worked into the whole. Their shapes and shadings reveal further details in the complete scheme Tolkien planned.

But like individual mosaic stones, the scenes themselves merit attention. There are episodes here which will move profoundly even the newcomer to Tolkien. Such scenes, Christopher writes, should vastly outweigh the incomplete form of these tales. Among others, Christopher cites Gandalf's baiting of the lordly Saruman at the meeting of the White Council in the year 2851, and the arising of Ulmo Lord of Waters out of the sea at Vinyamar. Christopher might also have included Gandalf's efforts to persuade Thorin Oakenshield to accept Bilbo as guide; Tolkien's description of Isildur after losing the ring: "There he rose up out of the water: only a mortal man, a small creature lost and abandoned in the wilds of Middle-earth."

And certainly Turambar's slaying of the dragon Glaurung ranks as one of the great dragon scenes in the literature of the wicked worm. An agent of evil, Glaurung devastates the land, his stench foul and overpowering. Dizzied by Glaurung's reek, retching, hanging by a burnt tree in a ravine, Turambar draws the Black Sword of Beleg and thrusts "upwards with all the might of his arm, and of his hate, and the deadly blade, long and greedy, went into the belly even to its hilts. Then Glaurung, feeling his death-pang, gave forth a scream, whereat all the woods were shaken, and the watchers at Nen Girith were aghast."

In the light of the nearly insurmountable difficulties with the text -- makeshift, at times undecipherable, occasionally consisting of the barest outline -- Christopher Tolkien has performed brilliant editorial work. In brief introductions, in footnotes and in an appendix, Chiristopher explains, elucidates, connects. Tolkien himself informally dubbed his son official guardian of Middle-earth, describing the boy Christopher, the most frequent listener to his father's stories, as "nervy, irritable, cross-grained, self-tormenting, cheeky. . . . Yet . . . intensely loveable . . . to me at any rate, from the very similarity between us."

Is there more of Tolkien to follow? In his lifetime Tolkien was deluged by requests to create an elfish grammar, musical scores, more accurate descriptions of plants and terrain, more detailed maps. Since Tolkien's death in 1973, with the posthumous publication of "The Silmarillion" and now with "Unfinished Tales," interest has been rekindled and should continue to increase. Very likely, the high adventure in Tolkien's realms of gold has only begun.