PEGGY; The Wayward Guggenheim. By Jacqueline Bograd Weld. Dutton. 493 pp. $24.95.

THE FLAVOR of this biography and its continually split focus defy description. Direct quotation may suggest why: "Peggy was all too happy to . . . jump into bed with Brancusi, especially as she hoped he might give her a discount on his Bird in Space, a soaring bronze he envisioned as a 'project for a Bird, which if enlarged, would fill the sky.' Much influenced by the 11th-century Tibetan monk Milarepa, Brancusi felt 'a true form ought to suggest infinity.'"

Not much later: "'Max was sitting on a sofa,' continued Pierre Matisse, 'and Clement Greenberg comes in and says: "You're Max Ernst?" Wham! They start to fight.'"

"Hitler's entry into the vast frozen plains of Russia had proved to be the death knell of the Third Reich. The Allies liberated Paris in August 1944. By January 1945, the Russians were in Cracow and German troops were retreating toward the Reich. By March, General Patton had crossed the Rhine."

As a crash course in World War II and other phenomena incidental to the progress of an uncertain but determined collector, Peggy: The Wayward Guggenheim has a marginal fascination. But as a sampling of its chapter headings indicates ("My Heart Belongs to Dada," "Out of Her Head," "Life With Tarzan"), it is an otherwise frivolous biography of a notable woman whose career, treated as a libidinous case history, would be more accurately, and surely more generously, regarded as a lively footnote to recent art history.

Peggy Guggenheim was a woman of small size, no humor and little comprehension ("I whirled through life in a kind of dream," she said in her last years, "I never quite realized what was happening") who lived in the reverberating shell of her own legend. To ccount for that legend is to assemble the few significant facts on which it is based, and then to surrender to the myth-making faculty which -- ignoring a hundred other women of greater accomplishment, grace and probity -- has fixed its sights on her.

She was born into a family of robber baron brothers, one of whom, her father Benjamin, foundered with the Titanic. Without formal education of any substance, Peggy showed an early distaste for the "stupid, staid, bourgeois" people who made up the extensive Guggenheim clan and, still a teen-ager, began a long campaign of rebellion by "shaving her eyebrows and painting the toilet seat red."

This campaign soon took more sophisticated forms: eccentric high fashion dress; scandalous deportment; association, first, with Greenwich Village literati and then with the famous American expatriate colony on the Left Bank. After a number of short-lived domestic arrangements with members of the latter, Peggy, nearing 40, turned her attention to contemporary art and, under the tutelage of Marcel Duchamp, began the dual career as collector and gallery owner that would bring luster to her name.

HER FIRST gallery, Guggenheim Jeune, in London, provided her with an "official" window on the art world and gave a professional gloss to what was a curiously amateurish mixture of business and showmanship. Jeune was followed in 1942 by one of the most innovative galleries ever opened to the public -- Art of This Century. A kind of permanent happening, long before happenings became a season's entertainment, this series of obstacle course rooms on New York's 57th Street became a landmark for its unprecedented involvement of spectator with art object, exhibitions acquainting Americans with great but still unknown Europeans, and then for shows introducing Abstract Expressionism to everyone. What happened there within the short space of five seasons -- including the early or first appearances of Jackson Pollock, Hans Hofmann, William Baziotes, Robert Motherwell and David Hare -- remains an astonishment time has not modified.

When Peggy went to Venice in 1948 with the idea of staying, she soon found and bought the marble ruin of the Palazzo Venier dei Leone that would become her permanent home and exhibiting hall. The famous collection was still incomplete, but what she had by then amassed was of sufficient range and significance to hold its own (except in the regard of Venetians) on the same watery home ground with Tintoretto, Guardi and Canaletto.

As usual, this story is told in scatter shot detail. But the author's deeper interest lies in her subject's love life -- if that term does not overstate 40 years and more of spider-like sexuality which, we learn, accommodated liaisons, marriages, brief affairs with comely opportunists, transient studs, a few obliging women, and was without fastidiousness as to whether these partners came alone or with a friend.

Weld's broad research has clearly been an autodidact's picnic. But her tedious rehearsals of political history and her abecedarian's discourses on modern art are secondary to the remarks she has elicited from a precious few friends and a legion of foes. With the exception of Mary McCarthy, almost no one among the hundreds of individuals she interviewed seems to have retained the slightest degree of fondness for Peggy Guggenheim. And, on the evidence, no wonder. Peggy's acquaintances and lovers have contributed to these pages an incidental anthology of traducement Weld is at no pains to abbreviate or censor. Documentations of avarice, chintziness, disloyalty and wanton self-concern may satisfy a craven need to put one of the notorious and well-favored in her place. But the zeal with which rare snippets of praise are matched with their devastating qualifiers is apt to make readers wonder what impulse led Weld to choose a subject so vulnerable, and then to render that subject despicable.

Peggy's museum in Venice, an adjunct to her uncle's Solomon R. Guggenheim Museum in New York, has the look of a whited sepulchre these days and, compared with the casual years when Peggy herself would sit in the garden entrance -- a quiet grey-haired clerk dispensing catalogues -- it functions with turnstile efficiency. No longer do visitors wander into Peggy's bedroom where her address book lay open beside the telephone, and two or three Lhasa Apsos might look up with rheumy Tibetan eyes and languid shakes of their invisible tails. No longer can "the last dogaressa" be seen sunbathing alone in a deck chair on the palazzo's vast roof, or stepping into a gondola oared by a youth in white livery and an aquamarine sash. But the paintings and sculptures are all there -- a pharaoh's treasure housed in a monument to a wayward little girl who keeps for herself the honor conspicuously absent from this depressing account of her life.