The inexhaustible, not to say imperturbable Helen Lawrenson (""Latins Are Lousy Lovers,"" 1936; Latins Are Still Lousy Lovers, 1968) didn't tell nearly all in Stranger at the Party. Here, with only passing mention of days and nights with CondÃ‰ Nast, happy marriage to longshore-organizer Jack Lawrenson, she expands on whorehouses as hangouts (""you can always get a drink""), practicing to make perfect oral love (worldly boyfriend Freddie advised a banana, ""the idea being not to leave any teeth marks on it""), how to get a start in journalism (""Rule one: find a newspaper publisher who used to work for your father"") and how not to rise to the top. But if she kicked over jobs to, say, minister to an ailing Bernard Baruch in Austria, Lawrenson did become Esquire's top freelance contributor and a celebrity interviewer par excellence--not by persistence, she claims (""I'll take no for an answer""), but through the exhausting effort of establishing a rapport. Favorite interviewees include super-bright Mike Nichols, entertaining (""he does most of the talking"") David Niven, extra-sensual Yves Montand and--among the few women ""I really liked""--Marlene Dietrich, seen waiting for Lawrenson at the St. Regis ladies' bar. ""She wasn't in the least annoyed by my lateness. Her voice was low and slow, her manner quiet, her expression serene and amused, as if she had seen the rise and fall of empires and knew the score exactly."" Less winning is Lawrenson's total putdown of feminism, her naive (though now mixed) endorsement of Communism. And, when she writes straight on--about finding a home away from home in randy, pre-revolutionary Cuba or keeping house with her grandmother in LaFargeville (pop. 400), N.Y.--you wish for fewer snippets and more follow-through. But give Lawrenson her due: she's been rich and she's been poor, and rich, she'll tell you, isn't always better. She has a contagious zest for sex and a cheerful dirty tongue. For the woman of a certain age who knows that it didn't begin with Erica Jong--and latecomers to the all-hours party.