"Finishing the Hat": Stephen Sondheim's magnificent musical memoir: For a sizable tribe of acolytes, there is much to worship, analyze, and debate in the self-effacing but nonetheless magnificent, altar-like structure that is Stephen Sondheim's "Finishing the Hat." In the same way that his sharply psychological and intellectually (as well as tonally) challenging musicals created a new archetype for the Broadway theater, this consistently compelling book -- although burdened with an unfortunate spine-sprawling subhead that overly telegraphs his intent: "Collected Lyrics (1954-1981) with Attendant Comments, Principles, Heresies, Grudges, Whines and Anecdotes" -- attempts to define a new form for a musical memoir, one that weaves biography, commentary and exegesis. It succeeds with radiant intelligence and usually cheerful intensity; Sondheim writes with expected clarity and objectivity, but with an unexpectedly open and humble mien. The authorial voice is not that of a man with a brownstone full of accolades, but that of a man who has something meaningful he wants to pass along after more than a half-century of close observation and diligent participation.