Marianne Moore, a contemporary of Eliot, Pound and e.e. cummings, was one of the greatest American Modernists.

To readers already acquainted with her exacting and scrupulous poetry, this vast and ebullient selection spanning eight decades of correspondence - from the late 1890s almost up to her death in 1972 - will come as a surprise. In its sheer volume, for a start: this 550-page selection represents a mere toe in the water. According to the book's editors, no more than five per cent of the letters that she wrote during her lifetime have been gathered here. So, as the academic presses dig into it, this book will be supplemented by many others for a more specialist readership.

But there is something even more surprising than the quantity: the exact nature of its quality. It is not so much that Moore was a great and tireless letter-writer (at her most productive, she could write three of four letters a day to her own family) but that she wrote with a desperate and omnivorous appetite for every least detail of her life. Her Collected Poems - the book that any poet might hope to regard as the defining record of a life - suggest, by their sheer fastidiousness, that this might not have been so; that she might not have been such a marvellous gusher in prose.

What did she gush about? Animals, in particular - she was a fanatical zoo- and circus-goer; and clothes. Though not rich, she always dressed elegantly. Thanks to this correspondence, we learn how: her friends would give her things with which to make herself look as beautifully turned out as possible.

Moore wrote to everyone: relatives, friends, acquaintances, fans, literary people. People took to her and stuck like burrs. Many of her letters are almost too fanciful for words - especially the game-playing that she enjoyed with her brother and mother, forever giving them new pet names. Others are quite sober and brilliantly perceptive: her response to the young Allen Ginsberg, for example, who wrote to her enclosing a manuscript of his early poems in the 1950s. Although Moore responds somewhat in the manner of an elder stateswoman to a tyro, the letter proves how carefully she had considered his work. The young man would have had much to rage about - and much to be thankful for.

The other outstandingly trenchant literary letters are those to Ezra Pound. Moore abhorred Pound's anti-semitism and his often wild political judgments, but she treats him with friendly fairness, condemning him justly while maintaining respect for his intelligence, his erudition, and for the generosity he showed her when she was young and in need of advice.

This is an odd, eccentric, brilliant book by a poet whose talent to observe and describe what hopped, prowled and skittered in front of her nose - sometimes human, sometimes significantly less than human - is likely to remain unsurpassed.

Michael Glover