Kennedy and Swanson, as if We Didn’t Know : GLORIA AND JOE The Star-Crossed Love Affair of Gloria Swanson and Joe Kennedy <i> by Axel Madsen (William Morrow/Arbor House: $18.95; 328 pp., illustrated) </i>

Gloria Swanson didn’t appear to have much reason to embellish the truth when she claimed in “Swanson on Swanson,” an autobiography published by Random House in 1980, that she’d had a three-year love affair with Joseph P. Kennedy. By then, she’d had six husbands, including actor Wallace Beery, a French marquis and businessman Herbert K. Somborn, who used the money he received in their divorce settlement to open the Brown Derby restaurant. What did the actress have to gain by claiming yet another lover, even if he had been ambassador to the Court of St. James?

True, the news might boost sales of her book. But subsequent revelations have pretty much driven out any suspicions of literary opportunism.

The respected biographer, Doris Kearns Goodwin, noted in “The Fitzgeralds and the Kennedys” (Simon & Schuster, 1987), for example, that one of Rose Kennedy’s nieces had reported having overheard a fight between John F. Fitzgerald and his son-in-law over Swanson. It seems Fitzgerald threatened to tell Rose about the affair if Joe did not give Gloria up. “Undaunted, Joe threatened in turn that if Fitzgerald did tell Rose he would simply marry Gloria,” Goodwin wrote.

Now Axel Madsen has come forth with “Gloria and Joe,” a warmed-over canape tray of facts about the romance between the screen goddess of the 1920s and the patriarch of an American political dynasty. Based partly on the author’s 1974 interviews with Swanson, the book reveals far less about the couple than does either Swanson’s or Goodwin’s book.

“Gloria and Joe” begins with their meeting in 1927 in Manhattan over a lunch at which Swanson had sought financial advice from Kennedy, then the prime mover behind a film production company called Film Booking Offices. The book accepts Swanson’s contention that he quickly became her business partner and lover, then follows the couple around to Palm Beach, Hollywood, Paris, Cape Cod and other spots, until Kennedy walks out on her three years later.

The narrative alternates with background chapters on members of their circle, including Rose Kennedy and Erich Von Stroheim, who starred with Swanson in the film, “Queen Kelly,” a disastrous project engineered by Kennedy that turned into a “Heaven’s Gate” of its era. And along the way, the book occasionally dredges up facts worth remembering, such as that Rose’s father had a notorious affair with a cigarette girl named Elizabeth (“Toodles”) Ryan that may have helped to reconcile her to living with infidelity, and that when Swanson moved to Hollywood, its biggest star was Francis X. Bushman, who “had a spotlight inside his lavender car that illuminated his famous profile when he drove at night.” Madsen also reminds readers that the more than 40 films made by Swanson included not just Mack Sennett comedies and Cecil B. DeMille extravaganzas but also “Sunset Boulevard,” which in 1950 earned her an Academy Award nomination for best actress.

However, “Gloria and Joe” soon begins to sink under its cliches, misrepresentations, pedestrian writing and lack of a consistent point of view. The author also of biographies of directors John Huston and Billy Wilder, Madsen refers to Swanson’s father as “Daddy,” repeatedly describes her crowd as “tony” in scenes occurring decades before the word was coined, and quotes not only from other biographies but also from such authorities as The Barnstable (Mass.) Patriot.

Nor are those the only forms of sloppiness. In a discussion of Joe Kennedy’s roots, Madsen calls the Boston Common the “Commons,” refers to a non-existent “West Side” of Boston when he apparently means its West End, and speaks of a ferry trip from the Boston neighborhood known as East Boston “to Boston,” which is akin to speaking of driving from Watts “to Los Angeles.”

In quoting from Swanson’s memoirs, he adds or removes punctuation marks, as though the actress herself couldn’t get it right. Swanson wrote that, just before their first sexual encounter, Kennedy said: “No longer, no longer. Now.” Madsen adds an exclamation point after the now, giving the event a more breathless quality than in her account.

All of it finally recalls a passage in “Swanson on Swanson,” in which the actress complained about reporters.

“They wanted to know whether I liked tall men or short men, how often I ate dessert, what my favorite breed of dog was, if I dyed my hair, what my favorite color was, if I got depressed on rainy days, what my favorite flower was, if I considered myself stuck up, if I thought So-and-so was a nice dresser, if I ever obeyed silly impulses . . . “ she wrote, adding that the resulting stories were “almost always exaggerated and almost never accurate.”

Kennedy died in 1969 and Swanson in 1983, so neither will face any more questions about their favorite dog breeds. But “Gloria and Joe” shows that some problems have followed them to the grave.