These letters, written between 1944 and 1976 (after screenwriter Johnson's greatest years in Hollywood), aren't really the writings of a ""social historian""--as Alistair Cooke claims in a fond foreword. But if the gossip and cheerful fun here never rise (or descend) to the Pepysian level, Johnson's good-hearted, common-sensical, down-home spirit is a nice contrast to the usual bitter/gushy tone of tinseltown coverage. ""If there was ever a couple that I don't care whether they get together, don't get together, or dive off of Mulholland Drive, it is George [Sanders] and Zsa Zsa."" So Johnson writes in '51, but he's generally an eager, if unsleazy, reporter of who's-going-with-whom. And he does wonders with what happened on New Year's Eve when Walter Wanger gave Mrs. Oscar Levant ""a small formal grope."" Only when writing to George S. Kaufman, however, does Johnson come up with a real comic setpiece: a hilarious prÃ‰cis of the soapy pie Letter from an Unknown Woman, followed by his proposed sequel--Collected Correspondence of an Unknown Woman. Elsewhere he's merely lightly sardonic, as when, circa 1952, he writes to Claudette Colbert that Jose Ferret ""is as innocent as a child of any Communist taint . . . and travelled for over two years in a show with Paul Robeson without knowing he was a Communist. I don't think he even knew he was colored."" Of most substantial interest: sketches of Marilyn Monroe--in '53 (""Talking to her is like talking to somebody underwater"") and after her death (""Marilyn had the intelligence to . . . respect intelligence but not enough to participate in it . . . she knew this and it was a destructive knowledge""); contrasted memories of Faulkner and Fitzgerald; sizings-up of Harold Ross and Dashiell Hammett; and glorious put-downs of Tallulah Bankhead, Clare Boothe Luce, and television. Too little about the actual work of screenwriting, but--with some lovely Benchleyesque flights (""if this letter is too long, tear it in half"") and solid (if stuffy) annotations--a warm, likable grab-bag of Hollywood impressions and apprehensions.