One of the unique voices in our century, James Merrill was known for his mastery of prosody; his ability to write books that were not just collected poems but unified works in which each individual poem contributed to the whole; and his astonishing evolution from the formalist lyric tradition that influenced his early work to the spiritual epics of his later career. Merrill's accomplishments were recognized with a Pulitzer Prize in 1977 for Divine Comedies and a National Book Critics Circle Award in 1983 for The Changing Light at Sandover.     In this meticulously researched, carefully argued work, Evans Lansing Smith argues that the nekyia, the circular Homeric narrative describing the descent into the underworld and reemergence in the same or similar place, confers shape and significance upon the entirety of James Merrill's poetry.   Smith illustrates how pervasive this myth is in Merrill's work - not just in The Changing Light at Sandover, where it naturally serves as the central premise of the entire trilogy, but in all of the poet's books, before and after that central text.     By focusing on the details of versification and prosody, Smith demonstrates the ingenious fusion of form and content that distinguishes Merrill as a poet. Moving beyond purely literary interpretations of the poetry, Smith illuminates the numerous allusions to music, art, theology, philosophy, religion, and mythology found throughout Merrill's work.