Forty years of producing highly reliable renderings of French and Spanish poetry and drama have culminated in what is bound to be hailed as Merwin's grandest translational accomplishment. Following on the heels of last year's The River Sound and the verse-novel The Folding Cliffs comes this deft and smooth interpretation of Dante's ""second kingdom in which the human spirit is made clean/ and becomes worthy to ascend to Heaven."" It is only fitting that a poet so absorbed in environmental concerns engage this most earthen section of the Commedia, with its suffering characters and unkind landscape bringing into view sharpened images of ancient and medieval political, moral and erotic life. At the book's center, love's visionary force is revealed in the simplest declarative tone: ""Neither Creator nor creature ever,"" Virgil instructs the wandering pilgrim, ""was without love, my son, whether/ natural or of the mind, and you know this."" Virgil's steady tutelage reaches its pinnacle in canto 22, where Statius quotes his messianic eclogue and Dante-as-poet absorbs lessons about writing poetry by overhearing their talk. Soon after his guide's dramatic departure, Dante's focus on nature gives way to the transcendent Beatrice. At its best, Merwin's characteristically open-ended syntax allows him to capture the charged encounter's troubling, if not terribly visceral, effects: ""so I broke under that heavy burden,/ with tears and sighs out of me pouring,/ and my voice collapsed as it was leaving."" This translation is something of a companion volume to Robert Pinsky's Inferno in the many ways it supercedes in elegance those of Singleton and Sinclair, which had been the last century's standards. (Apr.) FYI: Also in April, Copper Canyon will issue The First Four Books of Poems by Merwin, which includes his 1952 Yale Younger Poets volume, A Mask for Janus ($16 256p ISBN 1-55659-139-X).