Christmas weekend. Two families, two generations, ranging in age from 30 to 72, sitting around a fireplace in Wilton, Conn., trying to find a common bond while sipping drinks and munching on Jarlsburg cheese. Politics, careers, the weather and finally books.

Someone mentions "The Last Convertible," Anton Myrer's best-selling novel of a few seasons back, later turned into a made-for-television movie. Murmurs of delight over a shared experience: "Wonderful . . . I'd read it again . . . That was our generation . . . The characters were so real."

Many of the people in that suburban Connecticut living room will be tempted by Myrer's latest offering, "A Green Desire," either in $14.95 hardcover or in the paperback edition that will undoubtedly follow. Small wonder since "The Last Convertible" was the ideal sort of popular fiction -- a nostalgic remembrance of the war-torn Harvard Class of '44, vividly recreating an era without grappling with too many unpleasant truths.

This kind of bankable commercial reputation sells books. Unfortunately, "A Green Desire" is a mediocre and predictable historical novel with none of the freshness of detail, none of nuance of character, none of the elegiac sense of time and place that distinguished "The Last Convertible."

There may be a simple explanation for Myrer's fall from grace. He was himself a member of the Harvard Class of '44 and wrote his last novel out of the passions of personal experience. "A Green Desire" is set a generation earlier, and we are treated to a pop-historical account of the Roaring Twenties and the Great Depression.

"A Green Desire" is the tale of two brothers, Tipton and Chapin Ames, the offspring of an impoverished branch of a fine old Boston family. As teen-agers both brothers are given a chance to move to Beacon Hill under the custody of their very upper crust Aunt Serena. Chapin, who, of course, turns out to be a rotter, jumps at the chance. Tip, who personifies all the virtues of the hero of a Frank Capra movie, stalwartly decides to stay home with dear old Mom.

After Harvard, Chapin becomes a World War I flying ace, moves to New York, marries into a leading brokerage firm and before the Coolidge administration is over owns a "thirty-room estate out in Glen Cove, a thirty-eight foot sloop with teakwood decking . . . a Rolls Silver Ghost and a Packard Boattail Speedster."

Early on, Tip, who has the same genes but none of his brother's social advantages, takes to the road as a drummer, a traveling salesman hawking correspondence school courses. He's an instant success and soon is rewarded with his own sales force and the nickname "Schoolboy." Tip's feats of salesmanship give the novel an intermittent interest, but Myrer would have done better if he had reread Sinclair Lewis before trying to paint the commercial realities of the early '20s.

This being formula fiction both brothers, of course, fall in love with the same woman, Jophy Gaspa, the product of a long line of upstanding Portuguese fisherman on Cape Cod. Jophy is a beautiful, vibrant, exciting woman and in case we have any doubts, the author repeatedly tells us that "she could never resist, the impulsive, the unconventional. It was as if, swept on by the act itself, she needed to explore all the perimeters of the possible."

Almost seduced by the nefarious Chapin, discovering in just a nick of time that he was merely "toying with her, using her" in "some kind of dirty, empty game," Jophy marries Tip on the rebound. But one knows that the marriage will be troubled, especially after Tip moves to New York and begins working for his brother hawking investment trusts in the go-go days before the stock market crash. Chapin, despite his worldly success, continues to long for Jophy's "wild grace, her quicksilver vitality."

Bad historical novels seem compelled to serve up a steady diet of political and social cliche's. In the opening chapter of "A Green Desire," Aunt Serena announces, "It's 1911, Lottie. One ought to keep abreast of the times." Later we discover it's 1919 when Chapin's future wife intones, "Just wait till the Suffrage Amendment is passed. Then you'll see some changes." By the time we get to 1936, Chapin himself foresees the whole sweep of human history: "War's coming . . . Reoccupation of the Rhineland was the opening gun . . . Europe's at war right now -- they just don't know it."

Occasionally, Myrer stumbles over his historical details. He tries to capture the social chitchat of 1923 with characters expressing relief that Silent Cal Coolidge is now "in the oval office." There's only one small problem: the phrase "oval office" wasn't used until the 1930s.

But the real flaw of a novel like "A Green Desire" is the shallowness of its world view. Characters don't have personalities, they merely reflect their generation and their social class. Chapin is cold, unfeeling and manipulative because he was reared on Beacon Hill. Tip is faithful, loyal, honest because he has stayed in the commercial hotels of a growing America. Jophy is impetuous and sensual because her ancestors came from Portugal.

Toward the end of the novel, Tip and Jophy are entertaining their son Joey, a student at Harvard, and his date with tales of the life during Prohibition: "This set the kids off -- they'd been reading Scott Fitzgerald and they wanted to hear all about the wild Twenties, bathtub gin and Harlem and madcap frolics on the lawns of lush Long Island estates."

We, too, have read Scott Fitzgerald and long ago absorbed the obvious stories about the wild Twenties, bathtub gin and Harlem. That's why we demand a little more subtlety and insight from popular historical novels by authors who should know better.