An epistolary Stakhanovite

Editing the letters of literary modernists is a major industry. Vast stretches of scholarship are being poured into the collection, then the tidying-up, of scattered correspondence. This ill-paid task is gargantuan. Thanks to the climate-control and market lure of American libraries, bits of paper covered with the words of great ones survive in quantities undreamt of in the past. Early 20th-century authors, moreover, were prolific, relying on fast post rather than the telephone.

The editing difficulties are obvious. These letters were not written for publication, their authors were careless in spelling and punctuating. So an essential preliminary to edited letters is a statement of how punctuation and spelling errors have been silently corrected. Then the criteria for selection must be laid down. Editors must discard a great deal. What has been deemed too trivial? Or, if heirs are lurking, too personal? And what is the point: to know more about the artist's work or the life?

Marianne Moore presents a hard case. Poet, editor of the American literary magazine The Dial during the heyday of modernism, she was an epistolary Stakhanovite. Her lifetime's output was an estimated 30,000, with 50 on a good day. Fifty-four pages for just one letter was no problem. But it is a problem for her editors.

Bonnie Costello and her team declare that they have selected on the basis of thought or wit, rather than of biographical or bibliographical illumination. The reduction has left only 21 out of Moore's 100 letters to Ezra Pound, 26 out of the 500 to "Bryher", Winifred Ellerman. If literary detectives thus get short shrift, so too do hunters for the personality of a poet. These letters conceal Moore's inner life to the point of pathology.

Its surface is not without interest. Moore was a cheerful, hard-working, well-dressed, church-going Republican spinster whose first volume, Poems, was published in 1921; who was influenced by Pound, Yeats, Eliot and Lawrence; who encouraged younger poets such as Allen Ginsburg and Robert Lowell; who won, between 1951 and 1953, the Pultizer, National Book Award and Bollingen prizes and who buried her libido under a mound of images of animals, insects and exotic fruits.

S-e-x is rarely mentioned and, when it is, disapprovingly. Moore believed "that it is normal for young people to have a sentimental attitude to love and that it is abnormal for them to be aware of the sexual aspect of their relations". Suitors made her nervous. Life dealt Moore a bad card. Her father's nervous breakdown before her birth removed him from the scene. She never saw him. The surviving trio, mother, brother John and little sister, clung together for dear life, sheltered in the early years by Mrs Moore's clergyman father in Missouri, then by other relatives in Pennsylvania.

Parting - when John left to go to Yale and Marianne to Bryn Mawr - was so traumatic that, when separated, the three of them wrote each other several times a week until the end of their days. John managed to marry and become a clergyman, a chaplain in the US Navy. Marianne and her mother stayed together, sharing a flat and travelling together until Mrs Moore's death in 1947. The letters that bound them all are written in the private, whimsical code of a private world. Or zoo.

Moore, who took biology courses at Bryn Mawr, was obsessed with animals in any form. Descriptions of dogs and lions, even those on rugs and lamps, or in museum exhibits, fill these letters. A live tree-toad seen in Connecticut gets the full poetic treatment as if she were rehearsing phrases for her poetry, which she was. She called her beloved brother variously "Pidg", "Weaz" and "Fish"; also "Badger", "Impala" and "Warble". She refers to hands and feet as claws and paws. Her animal names for herself (always referred to as male) are "Mr Rat" "Fangs" "Gator" and "Rusty Mongoose". Mother was "Fawn", "Mouse", "Bunny" and "Bear".

The chronological division of a writer's life into its significant stages is another task required of the letters' editor. In her prefaces to each section, Costello adopts the circumspect persona of her subject. She calls attention to salient passages ahead, such as Moore's criticism of Pound's anti-Semitism. But she ignores the emotional subtext, such as the hatred that screams through Moore's bright word-play with her brother, especially when the game concerns "Mouse" or "Bear", their mother.

Moore and her mother could not live apart. Mother inspired daughter and rejoiced in her success. Daughter thought mother a great intellect - way over the heads of visitors like Faulkner. But caring for the old lady in the confines of their Brooklyn apartment where they spent much of the second half of their lives was no joke. To her brother, Moore confided how "Mouse" called her "Cry-baby; cry-baby" and how "Bear" threatened to kick her, or "fulminated & glared at me and kept showing the whites of its eyes & its bead teethI".

Even so, "Mr Rat" lived in terror that "my bear might depart the sanctuary". When Mary Warner Moore did die, her daughter, then 60, with foresight, had her own name engraved on the gravestone. However, a quarter century of productive life remained to her.

Collected and selected, the letters written over this long, useful life can be seen to lack the tension of Moore's witty, disciplined, metrically experimental poetry. They are, in this volume, made accessible by admirable apparatus (the glossary is essential) and by respectful scholarship. But in themselves, they are long-winded, fey and dull.

Brenda Maddox, whose biography of D. H. Lawrence won the Whitbread Biography Award in 1994, is completing a life of W. B. Yeats.