BEGINNING <i> by Kenneth Branagh (W. W. Norton: $19.95; 244 pp.) </i>

Kenneth Branagh--newly famous in the United States for his film “Henry V”--is brash to the very center of his being, but his vaulting ambition proves endearing; he immediately admits that while at 28 he knows little worth repeating, he’s happy to take the money offered for his autobiography to help subsidize his Renaissance Theatre Company. Branagh comes off like a young Welles--or a young Coppola, for that matter--but with a significant exception; he is less intent on serving his own vision than the Theatre itself.

It may be an act, but Branagh seems good company. Growing up poor near the docks of Belfast, Branagh came to love “the crack,” which he defines as “the Irish word for the pleasure of company, conversation, arguments and songs.” It’s not too much to say that “Beginning” is one long crack in which the reader can hardly catch his breath, for Branagh leaps from one story to the next as quickly as Gertrude marries Claudius. He’s made captain of the rugby and football teams at day school in England for “shouting theatrically butch encouragement to ‘my lads’ ”; at the Royal Academy of Dramatic Art in London, he turns down a major role in a BBC film in order to play Hamlet in a school production; at graduation he passes up understudying with the Royal Shakespeare Company to try out for the West End, succeeds, and finally agrees to join the RSC upon being allowed to play Henry V--at age 23. Branagh has a way of making these triumphs seem the only possible result of his vast enthusiasm for the acting profession.

That may sound boastful, but it isn’t. Branagh often reminds us that he’s plagued by guilt and fear . . . though of what, exactly, one can’t say. I’d guess that what terrifies him most is the fact that he has taken destiny into his own hands--has boot-strapped himself into fame and fortune by promising to do all kinds of things, then discovering he’d sooner fulfill a pledge than be called a liar. Branagh’s “blind and ridiculous faith,” his ability to talk with the “airy certainty of the blissfully ignorant,” is impossible to resist.