Marianne Moore made a new kind of verse, yet she denied that she was a poet. She worked with words: they were her trade. What she wrote was called poetry, she said, because there was no other category in which to put it. There are, in fact, no commonly accepted terms for describing the whole of her work and few accurate tags for designating the most radical forms she perfected. The verse received attention from the avant-garde poets and critics who were her contemporaries and from the generation of poets that followed them. She also became well-known, in the later years of her life, as an American eccentric who made "good copy," but her accomplished work baffled many readers. She continues, over a decade after her death, to be more highly regarded than widely read.

Moore's vision, a word that she would have thought too grand for the...