While it doesn’t actually prove that thesis, this is nevertheless a helpful compendium from Vanity Fair:
Ibiza was an earthly, if sin-soaked, paradise, but Irving, who had just turned 40, needed a pretext to get out of Eden in order to see his mistress, Nina, and disguise a midlife crisis. The Los Angeles Times’s critic had called him “America’s best worst-selling novelist.” He had just written Fake!, about an art forger on Ibiza, and had been filmed for what wound up as Orson Welles’s documentary F for Fake. Irving’s research for that book, together with a piece he read in Newsweek about Howard Hughes, gave him an idea for a perfect ploy. He’d write a phony memoir of Hughes, a man who was sufficiently famous enough that a purported “autobiography” was certain to be a best-seller, and yet so press-averse that he’d never come out of hiding to denounce it. “What a great book could be done, what a great character could be created!” he told his Ibiza neighbor Richard Suskind, the children’s-book author. It would be a victimless crime perpetrated on his publisher that would conveniently enable Irving to perpetrate a secondary hoax on his wife Edith. (…)
On a visit to his publisher at the McGraw-Hill Building in Rockefeller Center, Irving came into possession of a draft memoir by a Hughes associate and worked all the best bits into his own manuscript. Irving walked across the street to the offices of Time and Life—the very company that was paying him $200,000 for serial rights to the book—and speed-read the contents of a giant file of press clips about Hughes in the company’s “morgue,” and raided them to spice up his text. To add drama, he had Hughes meet Albert Schweitzer and Ernest Hemingway and run guns in World War II. He even threw in a regular-guy introduction in which he told how he’d come to know Hughes, how he got tapped to write the autobiography, and how he overcame his suspicion that the strange man was pulling a hoax on him. Then he modestly stepped aside. “Howard Hughes,” he declared, “can speak for himself.” (A caveat: much of the above narrative comes from Irving’s own memoir: an account of a hoaxer by a writer who, for a time, became a hoaxer. And while it is certainly plausible, the tale, for all we know, could be itself embellished.)
Not to be confused with…