NONFICTION : ONWARD AND UPWARD: A BIOGRAPHY OF KATHARINE S. WHITE by Linda H. Davis (Harper & Row: $22.95; 304 pp., illustrated).

She “more than any other editor except Harold Ross himself . . . gave The New Yorker its shape, and set it on its course.” So said Ross’ lately deposed longtime successor William Shawn. It may be so. The magazine’s own editorial voice was probably most influenced by E. B. White, whom Katharine Sergeant Angell met and married in their early days at the young publication. Her own elegant and firm-voiced writing surfaced rarely, in long collective reviews of children’s books and works on gardens and gardening.

But as the fiction editor (primarily), collaborating with other writers, from John O’Hara to John Updike by way of Mary McCarthy and Vladimir Nabokov, she undoubtedly did much to define “The New Yorker story” (a phrase she hated and a categorizing she denied). But her perfectionist zeal in matters as minute as the placement of commas is a tradition that endures at the magazine. She had joined the struggling New Yorker in 1925 and continued to advise, edit and do occasional articles even after illness forced her to leave in 1960. She died in 1977.

In this loving but candid biography by Davis, who became a family friend during the Whites’ last ailing years in Maine, Katharine emerges as a mixture of Manhattan toughness and New England graciousness, a strong and independent-minded early careerist who did not always balance well the demands of children and work. She was beautiful, statuesque, imperious and not always loved, although one wit named her “a velvet hand in an iron glove.”

By a sad irony, the meticulous editor that White always was would have taken a heavy pencil to Davis’ earnest but labored and awkwardly written book, her first. Katharine’s last years are a wearying chronicle of illnesses that were real enough but loudly borne. Part of the biographer’s dilemma is that great editing is invisible and all but impossible to discuss because the resulting prose carries a kind of fine inevitability. It’s the absence of an adequate editor that hangs out like a dangling participle.