Ithaca consists of sixty sonnets divided into two equal parts, "Ithaca" and "Gifts Reserved for Age." In Homer's Odyssey, Ithaca is the island home to which the hero returns after twenty years of war and perilous adventures. In Lehman's "Ithaca" sequence, two phrases are strategically repeated, with variations: "Happy the man who . . ." and "What did he believe in?"            In "Gifts Reserved for Age," the restless traveler continues to recollect and make sense of his life. Ultimate questions are raised: Does God exist? Can art redeem reality and not just contrive ways to escape from it? What are the compensatory "gifts" that accompany growing old?            Lehman, who has resided for many years in Ithaca, New York, does inventive things with the sonnet as a form and the sonnet sequence as the organizing principle of a unified book. Rich in allusion, not only to Homer's epic but to a shelf of important writers and thinkers, Ithaca is a witty and erudite book for grown-up readers who look to poetry for inspiration, profundity, and intellectual stimulation.