Asked by the editors of the New York Times Book Review … to explain how he became a writer, John Barth gave a surprising answer. "It is my fate and equally my sister's to have been born opposite-sex twins, between whom everything went without saying." But "after circumstances and physical maturation" separated him from his sister, Barth was forced to sail belatedly into society on the changeable winds of language, "talking to the Others, talking to oneself."

Coming from a student or critic, that sort of analysis would undoubtedly seem far-fetched, yet it works as the key to Barth's latest novel, Sabbatical: A Romance. There, Fenwick Turner, the 50-year-old narrator, himself a twin, preaches to his 32-year-old wife, Susan, another narrator, also a twin, that "we literal twins … are each of us the fallen moiety of a once-seamless whole … and our habit of wholeness ought to make us ideal...