The title of this story collection, as you might guess with Penelope Gilliatt--screenwriter of Sunday Bloody Sunday, maddeningly oblique film critic--is ironic. But not entirely. Splendid lives? A woman whose week, whose home, whose family is molded around her obsessive devotion to catering weddings at the community hall? A wife-supported, selfish senior citizen who has retreated into the home carpentry shop where he churns out wobbly cocktail cabinets? The fast-talking radio ""Phone-In"" host who dispenses instant cheer, hobby ideas, and mobile-home ads to his woebegone elderly callers? Splendid? Well, yes and no, since Gilliatt, while satirizing sterility wherever she sees it, can't help but salute joie de vivre--however unjustified--wherever it persists. In the most successful entertainments here, victims of Gilliatt's exposure and derision take on, almost against her will and ours, an odd heroism. Even the bloodless hollow men of academia, bland or cowardly, strangely survive the devastating diagnosis of ""There's something missing."" Less effective are the celebrations of too-obviously splendid lives, with the cards sentimentally stacked: an imitation Auntie Mame who impetuously spends her life savings on 37 N.Y.-to-Rome air fares, to rescue her grandson from his unfeeling father by keeping the boy in continual transit; ancient eccentrics with lovable wits and cutting insights; a spunky darling who throws over her pompous lord-of-the-manor young husband for his 62-year-old uncle (""Think of the fun we'll have before I kick the bucket""). In such over-easy exercises, Gilliatt must fall back on sheer stylishness to keep us edgily delighted, and this she has no trouble doing--with peripatetic clever talk, with quizzical ellipses, with quirky details, with screenplay-like montage. At her worst then, a glittery technician, representing the bright side of the limited New Yorker sensibility; at her best, leaving the twinkling and sighing behind, an honestly ambivalent observer of life, splendid and otherwise, who can move as well as dazzle.