THE LAST BLOSSOM on the Plum Tree takes place in the innocent late 1920s, when the rich could spend long, luxurious days preparing for their elegant nights and not be burdened by such petty annoyances as social consciences. It is nice to enter that world and be treated to the sight of old sour-puss Irma Shrewsbury as she develops a mad pash for Charlie Hopeland, an ambitious young lawyer who "played tennis, golf, and bridge, danced beautifully, and was exactly what a hostess wanted." It's even nicer to read about Irma's sister-in-law, the warm-hearted Emily Codway. Like Irma, Emily is a widow -- but what will be the result of her flirtation with the handsome Italian cosmopolite, Prince Carlo Pontevecchio?

In other words, The Last Blossom on the Plum Tree is a perfectly nice book. There was no need for its publishers and/or its author to equivocate and subtitle it "A Period Piece," as if seeking more gentle judgment than if it were called "A Novel." It is a novel, and a competently written one at that. Brooke Astor, who is well-known as a philanthropist and socialite, has produced a good-natured work about rich people.

The story is a pleasant one; the characters in it concern themselves with little more than clothes, social calendars, love affairs, and, not unexpectedly, their wealth. As the narrator observes about Irma: "What she really wanted was to live forever and keep her money to herself."

But for all its niceness, The Last Blossom on the Plum Tree is not one of those delicious souffle's of light fiction like Thorne Smith's Topper Takes a Trip, or E.F. Benson's Queen Lucia. And the reason is that Astor's writing is diffuse; often, there is no coherent point of view in the novel, no narrative thrust to draw the reader along. Instead, just as he is beginning to enjoy Emily's view of a world of properly written invitations and personal maids, the reader is pulled here, there and everywhere. Not only is he privy to Emily's thoughts, and Irma's, but he gets to know the viewpoints of at least six or seven other characters; that is six or seven too many. There is no single eye keen enough to observe that graceful world that (may have) once existed.

Because of this jumping about, there is no one character delineated well enough for the reader to care about, to root for throughout the novel. A protagonist need not be loveable -- or even admirable -- to arouse the reader's concern. But the reader ought to be able to want something for the hero or heroine. This holds true in all types of fiction: the comic as well as the serious. A protagonist may be so frothy as to make the foam on an ice cream soda seem leaden, but the reader still has to care enough to want to know: Will it all be okay? THE CHARACTERS in The Last Blossom on the Plum Tree are pleasantly rich, well-mannered enough not to dribble soup on the bodices of their Parisian gowns, and so well-traveled that the narrator can assert in the most charming, understated way: "Emily went to the Hassler, where she was known." But because the writing is often unfocused, the characters do not get the chance to really come to life. Emily has some wonderful moments. She demonstrates patience and droll humor with a fluff-headed actress, Molly; she is a paragon of courtesy toward that prize pill, Irma. But just as the reader is getting nicely settled down with Emily, the author yanks him off to another country, another character.

The writing then becomes more travelogue than narrative: "Day followed day. In Genoa they visited two places filled with Van Dykes -- Van Dyke lived in Genoa for several years and, as Carlo explained, painted the nobility. Then on to the cemetery with its outlandish tombstones. In Rapallo Emily met Max Beerbohm and his wife, Ezra Pound and Augustus John and the di Robilants, who had the most spectacularly lovely house in Rapallo. They even went on an all-day walk in the mountains behind Montallegro. These mountains, from which one saw Portofino, were the foothills of the Apennines, Carlo told her; and in the old days were hideouts for brigands."

Nevertheless, there are many instances of sharp, amusing observation. Writing of a woman in love with a pretentious writer: "About once a month he had these moods, rather like a woman having her period. She usually paid no attention to them. They were especially bad if he was reading a book that was better than one he could ever write. So she forgave him for his present bad temper, thinking that Tolstoy was very strong competition."

There are many charming asides as well. "Emily, still alluring at forty-nine (the official age she had chosen since the death of her husband) looked at Irma and thought a woman will not die from lack of love, but she will certainly wilt."

So while Brooke Astor's novel is not a comic tour-de-force, it is a likeable book. Its people are not the name-dropping, label-dropping, cold-blooded acquisitors of much of the current Rich Fiction: all those Hollywood/Riviera/New York novels where characters with names like Trask, drive Maseratis, where Nikkis wear Fendis with their Claude Montanas and where Daphne's breasts are described in language better suited to the produce section of Balduccis.

No, Brooke Astor's rich people are nice, decent -- pleasant company. And so is The Last Blossom on the Plum Tree. Susan Isaacs is the author of "Compromising Positions," "Close Relations" and "Almost Paradise." She is working on her fourth novel.