REBECCA WEST This Is What Matters By Victoria Glendinning Knopf. 300 pp. $19.95

AMONG THE endowments a writer might wish for, surely wit is near the top of the list. Regular delivery of bons mots -- especially the biting kind -- tempts editors to find space for you and prompts readers to note your name. Dame Rebecca West had wit inexhaustible and deployed it on a great variety of topics throughout her years as a professional writer -- all 72 of them.

She compared the meagre mind of the abdicating King Edward VIII to a "telephone exchange with not enough subscribers." After Evelyn Waugh converted to Catholicism, she said he "made drunkenness cute and chic, and then took to religion, simply to have the most expensive carpet of all to be sick on." Widening her scope, she wrote: "There is, of course, no reason for the existence of the male sex except that one sometimes needs help with moving the piano." It was as a scathing feminist, in fact, that she made her earliest mark, with the reviews and commentary she wrote for the British periodical The Freewoman.

These and other sallies pepper Victoria Glendinning's biography of the writer she once called "the most interesting woman of this century in England." Glendinning specializes in Lives of Female Greats -- Edith Sitwell, Vita Sackville-West, Elizabeth Bowen. She knew Rebecca West, and the new book evinces a rapport between biographer and subject that sets it above the others, excellent though they are. Yet Glendinning seems to have resisted temptations -- and there must have been many -- to soften her judgments for the sake of memorializing a friendship.

West was born Cicely Fairfield in 1892. Her mother was a gifted amateur pianist, her father a brilliant but feckless journalist who ditched the family when Cissie was 8. (The same parental pattern shapes The Fountain Overflows, West's finest novel.) Though their background was genteel and their braininess soon manifest, Cissie and her two sisters grew up "without acknowledged status in any section of the community" -- a distinct handicap in class-fettered Edwardian England.

She adopted her pseudonym in the early months of her writing career, to spare her mother's antifeminist sensibilities. (The name comes from a stormy character in Ibsen's play Rosmersholm.) She met H.G. Wells, then at the zenith of his fame, and became his lover. He was her "Jaguar," she his "Panther," and they conceived a child. Already married to an indulgent woman, Wells had no intention of disrupting an arrangement that gave him the comforts of home and countenanced his sexual roving. Young Anthony Panther West grew up seeing his father only occasionally and living with a mother who pretended to be his aunt in the interest of propriety.

When, after 10 fractious years, the affair with Wells ended, West entered into a brief, disastrous liaison with the press magnate, Lord Beaverbrook. His impotence -- along with a few other sexual fiascos -- undermined her feminine self-esteem. She feared she had developed into that stereotype of antifeminist propaganda, a castrating bitch.

Glendinning offers this period of maladjustment, during which West underwent psychoanalysis, by way of explaining her surprising marriage to Henry Andrews, a banker. Contrary to popular belief, she supported him at first; later he came into a legacy that enabled them to live like rural squires. At best, Henry was merely dull -- "such dead, though excellent, mutton," Virginia Woolf called him. In his old age his dottiness and reckless driving sorely tried Rebecca, and when he died in 1968 she felt relief. In retrospect, however, she decided that as marriages go it had been a good one.

Anthony, now aware of his identity, didn't take to Henry. And his mother meddled in Anthony's life -- by trying to patch up his first marriage, for example. There ensued one of the most articulate feuds in literary history -- Anthony humiliating his mother by thinly disguising her as a selfish actress in his autobiographical novel Heritage; the two of them bickering over punctilios of family history in the pages of Harper's; Anthony having the last, unanswerable word after her death in a new introduction to Heritage, where he depicts her as a prodigy of apoplectic egotism. Glendinning cannily sums up their brawling as a "vendetta {that} was in a perverse and obscure way transformed into a source of psychological justification, even a source of energy, by both of them."

GLENDINNING KNEW Rebecca West in her grande damehood: best-selling novelist; proto-New Journalist who covered the Nuremberg Trials for The New Yorker; author of the mammoth, genre-bursting travel book Black Lamb and Grey Falcon; and peerless raconteur. The book closes with a vignette -- both triste and tonic -- of the panther in extreme old age (she died in 1983, at 90). "Her visitors . . . waiting in the drawing room {of her London apartment} might be disturbed by loud groans of 'Oh God, oh God' from the bedroom, as Dame Rebecca divested herself of the old dressing-gown in which she worked and strove to dress herself, crippled by arthritis, in pain from diverticulitis; 'Oh God, oh God' again as, with her housekeeper's help, she rummaged for her hearing-aid and the right pair of spectacles. But then Dame Rebecca made her entrance, in a gold-braided kaftan, supported on a malacca cane, two or three pairs of spectacles swinging on cords around her neck, and proceeded to give the visitor the time of his life. It was hard to leave, and she would limp to the door to see her guest out -- the impossible questions, the imperious opinions, and the laughter still pouring from her. Only when the door closed did the power cut out, and Dame Rebecca collapsed into grey exhaustion."

As captured in this balanced, stylish biography, Rebecca West seems not only "the most interesting woman of this century in England" but also the most vital.

Dennis Drabelle is a Washington writer and editor.