SINCE ITS PUBLICATION FIVE DECADES AGO, William L. Shirer's monumental study of Hitler's empire has been widely acclaimed as the definitive record of the twentieth century's blackest hours. A worldwide bestseller with millions of copies in print, "The Rise and Fall of the Third Reich "offers an unparalleled and thrillingly told examination of how Adolf Hitler nearly succeeded in conquering the world. Here, in a thoughtful new introduction for the fiftieth anniversary of its National Book Award win, Ron Rosenbaum, author of the much-admired "Explaining Hitler, "takes a fresh and penetrating look at this vital and enduring classic and the role it continues to play in today's discussions of the history of Nazi Germany.