APART FROM the evanescent interest inspired by Visconti's ghastly film version of Death in Venice, the novels and stories of Thomas Mann gather too much dust these days. Perhaps an age that likes its stories passionate and obvious is a bit repelled by the pervasive irony, the "elegant equilibrium" in Richard Winston's phrase, of Mann's tone. Mann was a comedian in the ancient sense; his sensibility simultaneously embraced, without scorn, all the contradictions woven into the fabric of life.

Winston's brilliant study, left unfinished by his untimely death of cancer two years ago, should stir an overdue revival. Winston was not the first critical biographer to seek out "the making of an artist"; but he is one of the few whose skills justify so bold a claim.

Whatever artistry was latent in Thomas Mann's high- bourgeois North German heritage--the writing gene must have been there from the first in view of the comparable if less celebrated talent of his older brother Heinrich--there was every family impulse to suppress it. Mann's authoritative father, the last of a long, imposing line of Lubeck merchant-princes, was not exactly hostile to art. But unless a talent were first-rate, he considered that it led only to Bohemia. Thomas, an indifferent student who failed to qualify for university matriculation, seemed to fall short of genius and in his late teens, was apprenticed at an insurance firm. He was later to describe himself as "almost inconceivably ill- educated . . . a hopeless lazybones." By the demanding standards of high Germanic scholarship, that was true enough but also irrelevant. Formal learning is rarely decisive for a writer. What counts is a talent for using experience or learning, as Mann was to do so brilliantly in novels like Doctor Faustus and Joseph and His Brothers.

In the period covered by Winston's volume--that is, to Mann's 36th year in 1911--Thomas Mann produced two works indisputably great: the long novel Buddenbrooks and the novella Death in Venice. In quest of material for Buddenbrooks, a study of a family in decline through four generations (the essence of the decline being the attenuation of the acquisitive drive by art and sensibility) Mann combed family archives and recollections and wove them, sometimes verbatim, into the tale. For Death in Venice the materials fell uncannily to his hand during a family trip--even to the model for the beautiful Tadzio who fatally bewitches Gustave von Aschenbach. (Years later, well after Mann's death, he identified himself as a Polish count living in Warsaw.)

Allied to this skill at using autobiographical materials (and even friends and relatives, unsparingly observed) there was an unusual assortment of tensions useful to the storyteller. There was the family commercial heritage, at war with a beckoning life of art; there was the bourgeois at war with the bohemian, the sedate North against the playful South: Lubeck against Venice; there was the Apollonian principle of order versus the lure of Dionysian revels. To have managed these powerful themes freshly, without pedantry or didacticism, is one measure of Mann's greatness.

There were other, more subtle and problematical tensions in Mann's work as well, and Winston discusses them with exquisite skill and tact--and plausibility. Mann and his brother Heinrich were friends and rivals who parted ways on a number of issues of craft, so much so at times that Thomas once exclaimed that the only suitable word for his feeling was "hatred" of "the aesthetic iciness, the funereally cold wind, that blows from his (Heinrich's) books." The brotherly rivalries so brilliantly observed in the Joseph tetralogy no doubt had some foundation here.

Thomas Mann, moreover, was a self-declared "philo- Semite" in a society marred by anti-Semitism. And a fascination with the homoerotic runs through many of his tales.

Neither of the latter preoccupations, as Winston shows, was strange to the Germany of Mann's youth. That age was already caught up in the complex tensions of the "Jewish question" that later ripened so disastrously under Hitler. Mann, who had married Katia Pringsheim, the daughter of a prominent and wealthy Jewish professorial family, would later affirm a wider humanity. But his youthful experiments in portraiture (e.g., "The Blood of the Walsungs") were controversial from almost every point of view.

In certain literary circles of turn-of-the-century Munich, centered around the poet Stefan George, there was an unabashed cult of platonic homoeroticism. Mann, of course, plumbed this obsession in Death in Venice, and according to Winston even confided to his diaries an intriguing hint of "inversion" in his own case. Indeed, considering that Mann's most imposing work, the story of Joseph and his brothers, is a long reflection on the Jewish destiny, and that Death in Venice is as deep and subtle an exploration of the homoerotic as exists in 20th-century fiction, not the least of Mann's claims is an unsparing artistic courage. Winston's exploration of these troublesome themes is neither prurient nor prudish, and highly instructive.

Alas, Winston's projected biography was cut short just as he reached the crucial midpoint of Mann's career. So we have only a tantalizing fragment of what would surely have been an imposing work. But even these brief pages remind us of the brilliance and depth of this greatest of 20th-century German storytellers, who with Proust, Joyce, James and Faulkner, was a primal force in shaping the 20th-century novel: a mold of form against which succeeding works of fiction must be measured.