HISTORIES ARE WRITTEN in two distinct forms, depending on whether they are directed toward a scholarly or a popular audience. Among professional historians only the scholarly form that walks the narrow, empirical path and eschews all romance is accorded recognition as History. However, for the common reader, you and me, it is mainly the second form -- narrative history with a high imaginative component -- by which he forms a comprehensive vision of past ages. Since Walter Scott a good proportion of the best narrative histories have taken the form of the novel, the form best suited to framing alternate (mental) realities on the scale required.

Historical novels are most often praised or dismissed as novels, but surely it is their power as narrative history that is their main strength, the power to evoke the feel of ages lost to memory. No one who has fallen under the influence of Mary Renault's The King Must Die can escape the patterning power of her account of Bronze Age Greece, and the huge popularity of Herman Wouk's World War II novels is due at least as much to their lucid, human-scaled ordering of a welter of historical "facts" as to their skill in spinning a melodramatic yarn.

So it is with Gary Jenning's Aztec. As a novel it should satisfy all but the most finicking literary appetite. The prose is smooth, a transparency one quickly ceases to take account of. If it seldom wakens thunders of the epic deep, it does at least avoid the Muzak-like monotony of James Michener's Basic English. The plot has just enough momentum to keep the pages turning, but since Aztec is essentially a picaresque narrative, it doesn't build to a dramatic climax proportioned to the grandeur of the historical events. Of its characters those that seem most plausible as human beings (i.e., most like us) are most dubious as representatives of Aztec civilization.

Fortunately, however, the converse is not true. The social panorama of pre-Columbian Mexico that we view through the narrator's eyes registers as alien and credible in an ever-accruing multitude of humanly significant details. Aztec deserves to supplant Prescott's The Conquest of Mexico as the Authorized Popular Version of one of history's most awesome confrontations. One reason for Jennings's success (apart from the 10 years of homework that have gone into his book) is that he has had the sound dramatic sense to tell his story from an Aztec point of view. Not that losers are necessarily more interesting than winners, but because for a human drama to exist the losers must have moral parity with the winners. They can't be gooks, dismissible by virtue of our refusal to understand them. Prescott, writing in 1943, viewed the conquest of Mexico as an instance of Manifest Destiny. He never stops admiring Cortez's spunk or deploring the iniquity of the Aztecs:

"Human sacrifices have been practised by many nations . . . but never by any, on a scale to be compared with those in Anahuac. The amount of victims immolated on its accursed altars would stagger the faith of the least scrupulous believer. Scarcely any author pretends to estimate the yearly sacrifices throughout the empire at less than twenty thousand, and some carry the number as high as fifty!"

Surely the Aztecs are to be reprobated, but an historian is obliged to try and understand them, as well. How, especially, are we to fathom the fact of their conquest by a mere 500 Spanish soldiers, without supplies, unable to speak the language, facing an enemy not only warlike but literally bloodthirsty? Consider, further, that while other conquerors have usually been assimilated, like the Normans, into the people and culture they have conquered, the Spanish were able very nearly to efface Aztec civilization, forging its shattered remnants into their own horrific utopia, a New Spain more perfectly Spanish than the Iberian peninsula could ever be made to become. How could such a fearful success issue from such small beginnings? Was it inevitable, given the superior technology -- guns, horses, sailing ships, the skill to work iron -- that Cortez commanded? Or was the Aztec leader Moctecuzoma chiefly to blame because he refused to exercise the advantage of his immeasurably greater numbers? (This is the assumption behind Peter Shaffer's The Royal Hunt of the Sun, a play of much tragic power, though less convincing, as historical argument, than Aztec. Or -- and this is Jennings' thesis -- was there a tragic flaw in the Aztec civilization itself that made it collapse as soon as the possibility of another social order was announced?

Jennings does not state his case so baldly. His narrator, Mixtli, is an Aztec Horatio Alger whose slow rise from scholarship student to the aristocracy allows him an inside view of the various cultures inhabiting the Mexican subcontinent in the decades before the Conquest. By the time Cortez's ships appear on the eastern horizon (four-fifths of the way through the book!) Mixtli has been a scribe, a pimp, a warrior, a merchant, and a privy councilor to two Revered Speakers (as the Aztecs styled their kings). He has also enjoyed amicable sexual relations with his sister, his servant, his wife (and her mother), and sundry women dotted like oases across the map of Mexico. To Jennings' credit be it said that he writes about the varieties of sexual experience without indulging fantasies of violence or rape, and that in depicting the gory details of the Aztec religion he keeps to the polite side of the line that separates morbid curiosity from salaciousness. Aztec is not a book for the squeamish, certainly, but neither does one feel a need to wash after reading it.

It is Mixtli's humorous, Scheherazade-like voice, as he narrates the story of his life to Spanish scribes, that keeps the book's 755 pages turning at a steady clip, but that voice -- and the character to be inferred from its inflections -- is also the book's chief stumbling block as a vision of history. Mixtli is too much a modern homme moyen sensuel to be believed in his role as an Aztec Everyman. He describes the Aztec rites of human sacrifice clinically, as one accustomed to being a frequent witness, but without reverence, fear or awe. We are informed of his entire intellectual history but are never shown the source of the skepticism that allows him at one of the book's most gruesome and dramatic moments to accomplish a revenge tantamount to the gravest sacrilege. Mixtli seems almost to know he's a rogue American, transported Connecticut-Yankee-style to the court of Moctecuzoma, so clearly does he order his account of Aztec culture for our reading convenience.

But one would have to be the purest of purists to allow that objection to stand in the way of reading what is an historical diorama of the broadest dimensions, a meditation on the human condition that bears pondering, and a story of unfailing (if variable) power to bind a spell.