That other Sitwell: Edith; Edith Sitwell: A Unicorn Among Lions, by Victoria Glendinning. New York: Alfred A. Knopf.$17.95; Edith Sitwell: A biography, by Geoffrey Elborn, New York: Doubleday & Co. $15. 95.

Many people, both during her lifetime and now, have found it difficult to take Edith Sitwell seriously. She devoted her life to writing poetry and promoting her own and other poets' work, and she ranks with Elizabeth Barret Browning, Christina Rossetti, and Emily Bronte as the only English women poets of note.

But her extravagant appearance, her aristocratic background, and the eccentricities of her personality made her seem to her critics a professional self-publicist, whose image people would remember but whose poems they would happily forget.

Regardless of the different opinions of her poetry, Edith Sitwell's life has enough unusual twists and turns plus enough humor and pathos to make an intriguing biography.

Victoria Glendinning and Geoffrey Elborn have finished neck and neck in the race for the first full-length study of Edith Sitwell's life. In previous biographies, Miss Sitwell has shared the attention of the biographer with her two brothers, Osbert and the outrageously named Sacheverell, both of whom were inextricably wound up in her existence.

"We all have the remote air of a legend," Edith said of her family in an autobiographical poem. This feel of exotic mystery derives partially from reality and partially from Edith's tendency -- agreed on by both biographers -- to embellish the truth about her childhood with imaginary gothic flourishes.

Glendinnings says that Edith's younger brother, Sacheverell, was skeptical about Edith's accounts of the miseries of her childhood. The two had very different impressions of their mother: Edith felt unwanted and claimed to have been cruelly imprisoned in an orthopedic device she called her "Bastille." Glendinning devotes proportionately more space to Edith's childhood than does Elborn, correctly in the case of a poet who drew many of her images from the world of the English aristocracy's green landscapes and gazebos.

Edith was born on Sept. 7, 1887, in Scarborough on the northwest coast of England and spent her difficult childhood in the austere grandeur of various family houses, particularly "Renishaw Hall" in Derbyshire. She never want to school, but was educated by nannies, one of whom -- Helen Roothman -- became a lifelong friend.

When she was 26, Edith moved to London with Helen Roothman and successfully launched a career in poetry. Though she contributed to the support of several friends throughout her life, Edith complained of chronic financial difficulties, the kind born of a family with too many beautiful old homes and not enough money to run them.

Edith discovered, in adolescence, that she was never going to be beautiful in the conventional sense. She decided to dramatize her tall, thin figure and her angular facial features into the bold facade that absorbed the world's attention. She achieved her exotic impression by wearing turbans, painting her nails pearly white, and dressing in brocade dresses.

But the private Edith Sitwell was very different from this flamboyant public image, as both Glendinning and Elborn explain. Her public persona, Glendinning says, "drove the private woman further and further into the shadows."

The central relationship in her private life was an intense but platonic association with the homosexual painter Pavel Tchelitchew.It occupies a considerable portion of both books, though the biographers are laboring under the handicap of being without Edith's letters to Tchelitchew, which are locked up in a Yale library until the year 2000.

Elborn handles the more difficult aspects of Edith's life, like this relationship -- and her hypersensitivity to personal and literary criticism -- in a less sentimental and apologetic tone than Glendinning.

Glendinning admits in the introduction to a "protective feeling" for her subject. this is perhaps what makes her portrait the more sensitive, and it is also nearly twice as long a book as Elborn's.

Both writers have produced creditable books, but neither work is authoritative, comprehensive, or conclusive as one would hope, given a subject whose life was composed of as many moods -- from circuslike gaiety to defeated loneliness -- as Edith Sitwell's.

Though Edith knew virtually every important literary figure from the dawn of her career to her death in 1964, and despite all the publicity she sought and won, she frequently acknowledged her unhappiness. Poetry and the self-built facade had not been enough.

As she wrote in the autobiographical poem "Colonel Fantock" of her childhood with her brothers: . . . we walked like shy gazellesm among the music of the thin flower bells.m and life still held some promise -- never askm Of what, -- but life seemed less a stranger, then,m Than ever after in this cold existence.m