Helen Fielding's Bridget Jones's Diary, an unabashed riff on Jane Austen's Pride and Prejudice, actually has more in common with Samuel Richardson's Clarissa. Where Bridget keeps us apprised of her flawed but persistent attempts at self-improvement in a year's worth of diary entries, the morally upright Clarissa wrestles with her love for the devious Lovelace in very private letters to friends and family. With both heroines, we feel like the favored confidante of someone more interesting than we are. Tennyson referred to Clarissa as a "large still book," and indeed, there's a stillness about most novels structured around letters and journals, no matter how lively the drama they expose. This may be why the audiocassette version of Bridget Jones's Diary sometimes seems shrill instead of earnest, petty instead of poignantly honest. As actress Tracie Bennett (Shirley Valentine) lifts Bridget Jones from the sanctity of the printed page, we find the cast of characters scratching at each other with the noisy exaggeration of a French farce. To her credit, Bennett infuses the dailiness of Bridget's life with admirable energy, shifting from Bridget's raspiness to Perpetua's cackle to Sharon's screech to Daniel's sneer with the ease of a stand-up comic. And here's one cassette that doesn't suffer from abridgment. What went flying by in written form--the shorthand minutia, the inventory of calories, the fluctuating cigarette consumption--