THE LOSER (308 pp.)Peter Ustinov Little, Brown ($4.50).
If Actor-Playwright Peter Ustinov were to ad-lib a novel on the stage or before a TV camera, it might turn out very well. With his wit, his storyteller's flair and his crafty talent for wedding the ridiculous to the dramatic, he might easily become an important prose bard. But Ustinov wants to write. While he did reasonably well in his engaging 1957 comedy, Romanoff and Juliet, he failed badly last year in his book of short stories. Add a Dash of Pity. To his credit, Ustinov refuses to quit: he has written a first...