Although this dual biography may try too hard to see the Brothers Mann as two sides of 20th-century Western Civilization--Hamilton often oversimplifies and exaggerates--there is indeed a resonant drama in the shifting artistic rivalries and political conflicts of writers Heinrich (1871-1950) and Thomas (1875-1955). ""You are both god-gifted boys, dear Heinrich,"" wrote Frau Mann to her eldest, but it was conservative, sensitive Thomas who won the early great acclaim--with Buddenbrooks in 1901, the expansive north-German saga of a middle-class, Mann-like clan. And by that time, cynical Heinrich had been only modestly praised for his more experimental social novels. Obvious cause for brotherly friction; but brotherly affection kept things in balance. . . till the Great War, when Thomas (""I hate democracy"") rallied to the Kaiser's cause while Heinrich poured his anti-war disgust into a 1915 essay on Zola. Thomas--egocentric, ""away on a cloud of his own""--took this diatribe personally (""the truly French spitefulness, the defamations and slanders"") and bid Heinrich farewell: ""Let the tragedy of our brotherhood take its course to the bitter end."" That's not what happened, however, because it is after World War I that the story really takes shape: Hamilton charts Thomas' ""gradual acknowledgment of the ideals which Heinrich stood for,"" ideals which became paramount with the rise of Hitler. Heinrich, of course, denounced Fascism from the start, but Thomas slowly became the more violently disillusioned expatriate--first cautiously silent in Switzerland (so that his books would remain available in Germany), then as a loud anti-German voice from Los Angeles. And, under the shadow of a final irony--McCarthyism--both brothers died abroad, Thomas a disgruntled U.S. citizen, Heinrich an ill, poor, and tragically mis-wed, California-based citizen of Czechoslovakia. Splendid, ironic stuff--but in order to highlight the brothers' political parallels, Hamilton sometimes fuzzes the chronology and falls short in areas that solo biographies would stress: the psychological insights are sketchy; family matters (Jewish wives, suicidal sisters and children) aren't integrated; the links between Thomas' political growth and his literary achievement often seem forced; and there's an unnecessary sprinkling of hyperbole (Thomas is ""the acknowledged spokesman of Western Civilization,"" Heinrich's ""the Schiller of modern Germany""). But, bristling with excerpts from eloquent, hurtful letters, this is a fascinating documentary--and a reminder of the need for a full-scale critical biography of brother Thomas.