She never made a movie. She never made a fuss--let alone a scandal. Thus, serenely stunning Kit Cornell from Buffalo, the quietly professional First Lady of the American Theater through the Thirties and Forties, is less well remembered than most great stars. And Mosel's respectful, thickly written, massively detailed biography tries bard to bring her back. ""Fighting off stardom the way other actors fight off failure,"" well-connected, slow-to-warm-up Kit delayed arrival in N.Y. till her mid-twenties (later she'd have to lie about her age). But once there, she soon drew acclaim playing, against type, a series of tarnished ladies; and she soon married, against her oppressive father's wishes, frail, brilliant, bisexual director Guthrie McClintic. Together they found more suitable plays for soulful Kit and produced them themselves in N.Y. and on tireless tour: Candida (five times, with Orson Welles, then Burgess Meredith, then Brando); Romeo and Juliet; and, above all, The Barretts of Wimpole Street. There's not much conflict, tension, or comedy in Kit's life story. Performing anxiety did give her psychosomatic pain, for which she summered in Germany; husband Guth and manager-secretary Gertrude Macy did squabble jealously over her; and perhaps there's pathos in Kit being ""squeezed out"" of the theater in the Fifties, forced to be content with her Martha's Vineyard retreat. But, as Mosel says, she reacted to the burdens of stardom by settling into ""a kind of smiling, gracious, and comfortable isolation."" As a result, even with Ms. Macy providing discreet insider details, this is undramatic but solid theater history, lighting up only on occasion, as with a one a.m. performance of Wimpole Street; Miss Cornell was one leading lady who was never good copy, just great theater.