"My experience with Sondheim musicals--and I expect that of most Sondheim enthusiasts--has inevitably been the same," New York Times theater critic Frank Rich once remarked. "One sits in a theater where people are cheering or sneering; the pitch and conflict of battle drift into intermission, where heated arguments ensue. At the packed closing performance of Follies at the Winter Garden in 1972, people threw flowers at the stage in the same theater where, only a week or so earlier, audiences had greeted the same production with indifference and coughing. At an early preview of Sweeney Todd (1979), dozens of unprepared theatergoers ran for the exits once it became apparent that cannibalism was on the evening's menu. At a final-week performance of the short-lived Merrily We Roll Along (1982), scattered clumps of theatergoers rose to give every song an ovation while the majority of the house looked on in perplexed, dumbfounded silence...