Orson Welles stayed away from Hollywood in the 1960s, having a laundry list of reasons to feel like a pariah. But when he returned in 1970, he found a film business newly receptive to rogue talent. It didn’t get more roguish than a 350-pound former boy genius seeking to make a barely describable film-within-a-film about a great man who has lost his creative powers.

Josh Karp’s lively but hyperbolic “Orson Welles’s Last Movie” describes how Welles got his foot into the door of the New Hollywood and his capacious body into a bungalow at the Beverly Hills Hotel, courtesy of BBS, the production company that had produced “Easy Rider.” He had agreed to adapt a novel, but he was really just using this perch for his own ends.

Welles began rounding up talent to work on “The Other Side of the Wind,” that dream project about the great man on the wane. Even Karp’s well-researched stories about how the crew was assembled have their magic. Gary Graver, a cameraman and Welles devotee, decided to cold-call him from Schwab’s drugstore, of all places; he guessed correctly that Welles would be at the Beverly Hills Hotel. And then Welles just hired him, saying that he was only the second cameraman to call and ask to work with him. The first had been Gregg Toland, who shot “Citizen Kane.”

Karp’s claim that the making of Welles’ last, sprawling, endlessly worked over and still unreleased film — it is being completed with the goal of a release this year, the centenary of Welles’ birth — “would prove to be one of the greatest Orson Welles stories of them all” is certainly supported by tales such as Graver’s. (His devotion to Welles was such that he went through multiple marriages while making the movie.)

Or Joseph McBride’s. McBride has gone on to become a film scholar and historian, but he was then a 23-year-old critic visiting Hollywood for the first time. He was working on a book about Welles and had gone to the Larry Edmunds Bookshop, a renowned mecca for film fans, where he got a phone number for Peter Bogdanovich, who was writing about Welles, too.

“Can you hold?” asked Bogdanovich, whose role in this story is central and all too poignantly Wellesian. “I’m on the phone with Orson.” The next day McBride was at a modest house where Welles was ensconced (his hotel charade was over) being greeted by his hero, who exclaimed, “Well, I finally meet my favorite critic!”

Sure enough, Welles had McBride’s first book of criticism on his mantel. During that dizzying afternoon, he was also cast in “The Other Side of the Wind.” He would play a nerdy, pompous critic. Like everyone else involved with this production, McBride was thrilled to go along for the ride. (McBride has described the experience in “What Ever Happened to Orson Welles?,” a much more insightful book about Welles, who died in 1985, than this is.)

The script had its genesis in a fight Welles had had with Ernest Hemingway, during which a lisping Welles mocked the macho author’s heterosexual posturing.

And its main character, Jake Hannaford, the waning director, seemed so autobiographical that many people close to the production assumed Welles would be playing him.

The role called for both swagger and despair and culminated in a denouement in which the filmmaker realizes that he is a closeted homosexual in love with his leading man. To make all of this work, Welles cast his friend John Huston, who’d never met a risk he wouldn’t take.

Other notable members of the cast included Oja Kodar, Welles’ beautiful young mistress he kept hidden from his wife, Paola; and Susan Strasberg, playing a harsh film critic who said of Hannaford: “What he creates he has to wreck. It’s a compulsion.”

One big question hovered over all of this: Would the film ever see the light of day? Welles had a history of making spectacularly bad choices when it came to financing his films, and this one remains the trophy-winner. The biggest problem it faced was funding from the Iranian royal family, which, once overthrown, had its assets appropriated by Ayatollah Khomeini’s regime.

That was a small blip compared with the troubles Welles himself created. He seemed not to want to finish the film and would never agree to a completion date, which kept him from raising enough money to get it done. He tinkered with it endlessly.

Much of this book, the part that isn’t mired in hopeless financial brambles, is devoted to the buoyant stories for which the film’s production will always be remembered. Rich Little, a member of the cast, remembered being introduced to Huston as the world’s greatest impressionist and being mistaken for a painter instead of a comic. Bogdanovich recalled Huston’s having no idea that he was a red-hot director, asking how many films he’d acted in; this was only the second. “Must make it very easy to count them” was the reply.

And Welles cannily fought off the idea that “The Other Side of the Wind” was autobiographical. He used this “Kane” reference: “You mustn’t look for keys. I never even went sledding.”