NIGEL HAMILTON has had the excellent idea of writing a dual biography of the renowned writers Heinrich and Thomas Mann. The basic point is not their physical relationship but that their talents and tastes complement each other, although often constrasting harshly. Heinrich was the social critic, a left liberal, at times a rather uncritical admirer of Western democracy and the Latin nations. Even after his conversion to democracy, Thomas was rather conservative, a German patriot as long as possible, a middle-of-the-roader, a believer in welfare measures but more concerned with "measure and value." Whereas Heinrich used a flashing, at times flashy, style, Thomas was the unrivaled master of 20th-century German prose. Where Heinrich wanted to change the world with his satires and manifestos, Thomas' major aim was to "tell it as it is" (sagen was ist ). After World War I, he too began to play a political role, but until 1930 he kept politics virtually separate from his fiction. Given these differences, it is not surprising that a state of fraternal love-hatred persisted for years.

Heinrich Mann has been largely neglected in the United States, and Hamilton's account of his life and works is most welcome. If Heinrich is not one of the very greatest of 20th-century German authors, he compares favorably with Hermann Hesse or Jacob Wassermann. A master of the grotesque, he may be ranked with another virtuoso of that mode, Guenter Grass. Heinrich Mann is both the more fertile and the more uneven of the two brothers. Among his most impressive works are the two slashing satires, The Blue Angel and Man of Straw , two other novels, The Little Town and Henri Quatre , and some fine essays.

Clearly, Hamilton's aims are laudable; we must turn to his execution. To begin with the positive: his shifts from one brother to the other are adroit. The historical background is well done, as is the account of the two Manns' very different attitudes during World War I: Heinrich was very much on the Western side, while Thomas carried on, an increasingly lonely defense of conservative Germany. Hamilton is of Heinrich's persuasion politically, but does not waver in his belief that Thomas was "the finest narrator in modern German letters." He includes striking remarks from both brother. Thomas on the intellectual role of the German Jews: "The critico-literary spirit of European democracy . . . is represented in Germany chiefly by Judaism." Heinrich on his enforced neglect of his fictional work: "But if people like me do not do their duty, who will be left?"

On the negative side: the author too often confuses literary and political values. He repeatedly overpraises some relatively weak works of Heinrich's because they are politically progressive. While he rightly implies that Thomas' political views were often mistaken, he accepts the aging novelist's petulant anti-Americanisms as if they had been handed down from Sinai. (Of course many things were very wrong in the United States around 1950, but Hamilton's comments lack proportion.) American resistance to the Berlin blockade is obliquely equated with "warmongering." Flying against the evidence, he maintains that Thomas Mann became "more" reactionary after his marriage; as Royal Highness shows, however, the opposite is true. He even bases statements on sheer assertion: thus the pleasant English girl with whom Mann was half in love in 1901 is alleged to reappear in The Magic Mountain (1924). But as what character?

A number of small mistakes increase one's doubts about this book. There are some bad slips in quotations from the German, and the names of two of the finest poets of the Manns's generation, George and Hofmannsthal, are each once misspelled. Who would expect that "Kant's practical mind" really refers to the Critique of Practical Reason , or that an expounder of German literature would write "Das" blaue Engel ? If many of the errors are not major, the number is still large enough to shake one's faith in the book. More serious are mistakes in describing the works themselves. Thus Thomas Mann's parodistic idyll "Song of the Child" is written not in blank verse but in dactylic hexameters. The short-lived magazine Spring Storm , of which he was the editor, was not "the school magazine" but rather an organ of adolescent protest, very much against the establishment. Perhaps some of these slips should be charged to an editor; but an author is basically responsible for his text.

A few of Hamilton's misjudgments and mistakes are horrendous. The Magic Mountain and Scott Fitzgerald's novels have very little in common. Yet that comparison seems harmless matched against the confusion of the renowned psychoanalyst Erik Erikson with a scribbler of the same name, the author of a cheap, vicious pamphlet against Thomas Mann. Hamilton has fallen into far too many pits. As Goethe said, there is no greater arrogance than pretending to comprehend the spirit before mastering the letter. CAPTION: Picture, Heinrich Mann (left) and Thomas Mann