In his 13 shows—he wrote only lyrics for three, music and lyrics for the rest—Sondheim has staked out a turf as big as the emotional landscape of post-World War II America. Even when the shows have been set abroad or in the past, their themes have addressed contemporary topics—or universal ones, Sondheim might aver—by way of metaphor. This is particularly true of the Sondheim shows since 1970. He has treated the travails of modern marriage in "Company," the corrosion of American optimism in "Follies," injustice and revenge in "Sweeney Todd," idealism and compromise in "Merrily We Roll Along" and Western imperialism in "Pacific Overtures." As Sondheim once put it, "I love to write in dark colors about gut feelings." (p. 25)

Sondheim has come to subsume all his influences so thoroughly that they cannot be readily identified in his work. He also has resisted any concession to...