IT IS A DARK TIME for Church and Empire. Europe is rotten with heresy; the false pope John XXII reigns in Avignon; Holy Roman Emperor Louis of Bavaria pursues the consolidation of his power in Italy. In north and south charismatic messiahs preach poverty, or debauchery, or revolution. Bogomils, Albigensians, Cathars, Dolcinians, Fraticelli, Spiritual Franciscans, Jews-- all are vilified, hunted down, tortured, burned by the Inquisition. It is widely believed that the trumpets of the Apocalypse are about to sound, the Seven Seals be opened. Was not the Emperor of the Last Days already born and perhaps even now in power at Avignon or Rome? For surely the world has turned upside down, surely the time of Antichrist has come round at last!

Such is the ominous backdrop of Umberto Eco's medieval thriller, The Name of the Rose, a novel of murder, politics and ideas that has rightly become an acclaimed European best seller.

Late in 1327 a Franciscan, William of Baskerville, accompanied by the novice Adso of Melk, journeys to an unnamed Benedictine monastery to arrange a meeting of d,etente between representatives of Pope John and Emperor Louis. Just as master and disciple arrive at the abbey, a young monk commits suicide under suspicious circumstances. The worldly abbot asks the Sherlock Holmes-like Franciscan--a disillusioned inquisitor and former pupil of Roger Bacon--to investigate the shadowy affair. To this end, William is granted free run of the establishment--except for the library, the finest in all Christendom. Malachi the librarian and his assistant prohibit any direct access to the fragile illuminated manuscripts. And if a man were to try to enter the locked tower rooms? "No one," replies the abbot, "even if he wished, would succeed. The library defends itself, immeasurable as the truth it houses, deceitful as the falsehood it preserves. A spiritual labyrinth, it is also a terrestrial labyrinth. You might enter and you might not emerge."

Ah, now that's the kind of demonic book room that Jorge Luis Borges might imagine. And indeed, William and Adso soon meet the ancient blind monk Jorge de Burgos, whose name and bookishness recall the Argentine fabulist (as does the novel's learned preface about how the author researched Adso's manuscript). Such homage whispers, sub rosa, that Eco's novel aims to be modernist as well as medieval, to reflect both the time of its action and the time of its telling. William, for example, embodies a spirit of tolerance and scientific inquiry, that of the approaching Renaissance; he consequently appears a relatively modern man surrounded by religious fanatics, many of these actual historical figures. In the course of his detecting this relentless bloodhound of Baskerville meets, for instance, the mystic Ubertino of Casale, the inquisitor Bernard of Gui, the general of the Franciscans Michael of Cesena, and followers of the Italian leveler, Fra Dolcino. Each of these believes he possesses the Truth; yet their voices and vociferations resonate in 20th-century ears with the stridency of born- again evangelicals, fascists, corporation climbers, Marxist fellow-travelers.

The mirroring of now-in-then seems peculiarly appropriate in The Name of the Rose for such a technique mimics the figural or typological thinking common to the Middle Ages. The Old Testament Job, in this view, is both himself and a type of the New Testament's suffering Christ; the offerings of the priest Melchisedek are historical yet also prefigure the bread and wine of the Last Supper. So too this novel can be read as a poetic synthesis of the early 14th century, and as oblique commentary on the excesses of the 20th. Adso, for instance, learns about the various cults that take fire from Joachim of Flora's vision of an earthly paradise, but modern readers also learn timeless character and appeal of a revolutionary ideology. Such rich, implicitly ironic textuality might be expected from Eco, a professor of semiotics at the University of Bologna; yet even his seemingly ultra-modern academic discipline finds its roots in monastic learning and patristic exegesis. The Bible and the Universe are God's two great scriptures, and in them we may read his message to the world-- though their intricate symbols must first be properly understood on several levels, including the anagogical and eschatological.

Especially the eschatological. For like the theological thrillers of Charles Williams, The Name of the Rose returns obsessively to John's vision of apocalypse. The various heresies that the monks practice or discuss-- and this is a talky novel, in the vein of Mann or Murdoch--all derive from a chiliastic forboding that traditional hierarchies are being upset by new ideas, new ways. The theme of The World Turned Upside Down occurs pervasively: in allusions to the topsy-turvy realms of Cockaigne, Saturnalia, the Coena Cypriani, and Carnival, in unnatural love between monks, in the leveling character of the various heretical movements, in the triumph of inductive reasoning over a priori reliance on received authority, in Aristotle deposing the Church Fathers, even in the new-fangled inventions that William makes passing mention of: gunpowder, the compass, spectacles, paper, the sextant, flying machines. All the signs suggest that breakup of the great chain of being which will herald the Last Days. Slyly, even the novel's preface alludes to such millennial fantasies, for Eco tells us that he "translated" this manuscript in 1968 --at the very time a youthful revolutionary populism was overturning the old order, hoping to forestall a fiery Armageddon and establish the new Jerusalem.

In his investigations William comes to realize that the secret of the abbey is somehow intertwined with the Biblical revelation to John. After the first death, there is a second, and a third; the murderer's modus operandi seems to derive from, almost to copy religiously, the opening of the Seven Seals. Even more disquieting, behind all the ritual killings looms a book, a book to rival the Ark of the Covenant in its awesome power. But to find that dread manuscript, William and Adso must penetrate the forbidden library, solve its riddles, and find their way to a hidden sanctum sanctorum.

Such Gothic hugger-mugger--part Borges, part John Dickson Carr--lightens Eco's operatic gravity, especially when the reader might begin to weary of visionary rapture or philosophical and theological wrangling. Number symbolism, alchemical secrets, the language of gems, pagan love charms, a linguistic Quasimodo, and the clockwork of a life ordered by the Benedictine rule further enhance the supernatural atmosphere. So too does the religious imagery, and the interlacing of vernacular and Vulgate. When Adso braves the library at night and surprises a beautiful girl, he is unsure whether she is the Whore of Babylon, the Woman Clothed with the Sun, or the devil in the flesh. When he gives way to her nakedness his ecstasy elicits the delirious language of the Song of Songs.

In its range, The Name of the Rose suggests an imaginative summa, an alchemical marriage of murder mystery and Christian mystery. It conveys remarkably the desperation of a dying culture, while at the same time touching on perennial issues of love, religion, scholarship and politics. Even an occasional reliance on coincidence and fortuitous revelation strengthen its medieval aura, its convincing re-creation of a way of life now lost. As Adso writes at the end of his chronicle--quoting a 12th-century poem about the passing of Babylon and Rome--Stat rosa pristina nomine, nomina nuda tenemus. The rose of yore is but a name, mere names are left to us. Yes and no, for through Umberto Eco's prodigious necromancy some of those names livkee again. Unforgettably.