Garbage," A.R. Ammons writes in this book-length poem, "has to be the poem of our time because / garbage is spiritual, believable enough / to get our attention, getting in the way..." Talky and playful, the couplets of the National Book Award-winning Garbage propel one through the trash dump of 20th-century meaning, as well as into the past and future, where "millennia jiggle in your eyes at night." This project, by turns wryly self-deprecating and densely philosophical, places Ammons in the company of such recent epic funnymen as John Ashbery, Ronald Johnson, and, very self-consciously, William Carlos Williams. Like any good epic, the poem begins in doubt, with Ammons wondering whether to write the book or simply retire and live a life of leisure on Social Security (plus a surely ample pension from his longtime Cornell University professorship). Like John Milton in the preamble to his epic, Paradise Lost, Ammons uses the metaphor of a tree to focus his poetic ambition. "I mean," he writes, "take my yard maple--put out in the free / and open--has overgrown, its trunk / split down from a high fork ... The fat tree, unable to stop pouring it on, overfed and overgrew ... It just / goes to show you: moderation imposed is better / than no moderation at all." Indeed, the poem's 121 pages seem at times nothing more than an attempt to buoy the moment between two extremes: exuberant falsehoods at one end of the scale, cynical platitudes on the other. This "moderation"