Another biography of Andy Warhol ? Is there really anything left to say about the pop artist whose images were so willfully ordinary - even banal - and whose few public pronouncements were even more mundane? Since Warhol's death 22 years ago, in addition to countless memoirs, documentaries, fictional recreations, posthumous diaries and critical studies - even a children's book  - we've seen at least four biographies, of which the new "Pop: The Genius of Andy Warhol" by Tony Scherman and David Dalton, is merely the latest, all telling the same story, yet each managing to find some small, previously unexposed aspect of an artist who was so cautious about revealing anything about his private life while he was alive.

Victor Bockris, a Punk-Pop-Bohemian Boswell, provided the basic details with his 1989 "The Life and Death of Andy Warhol" and Wayne Koestenbaum's slim 2001 biography revised Warhol's work through the fashionable gaze of queer studies, while Steven Watson's "Factory Made"  gave the most thorough account of Warhol as the central force behind the lives of the dozens of artists, actors and hangers-on  who inhabited his Factory in the 1960s.

Scherman and Dalton can't claim to staking new territory, but their book is strengthened by concentrating on Warhol as an artist, seen within the context of the changes that shook the gallery and museum world from the late '50s through most of the 1960s. Though it offers a brief treatment of Warhol's life before that time (he turned 32 in 1960) and of his last two decades as a walking advertisement for "Lifestyles of the Rich and Famous," their book defines him more particularly by emphasizing the years from 1961, when "Pop Art" was still new and undefined, through the spring of 1968, when his near-fatal shooting by an eccentric quasi-feminist symbolically put an end to his reign as Pop/Underground Scenemaker.

Already a celebrated and well-paid commercial illustrator by the end of the 1950s (specializing in shoes), Warhol desparately longed to cross over to the world of high art. Abstract Expressionism was waning and artists like Rauschenberg and Johns were exploring a style that rejected the purely formal drips and splatters of A.E. without returning to the naturalistic style that Pollack and Co. had rejected.

They developed the "Pop" themes by reproducing elements of the commercial culture around them, but Warhol broke apart by embracing a medium - silk-screening - that allowed both the authentic reproduction of any image and an artisanal division of labor that almost eliminated the personal effort of the painter, so romanticized by the abstract expressionists, to a job that could even be delegated to assistants. Mass imagery and mass production - soup cans and Brillo boxes - were the hallmarks of Warhol's art.

By 1963, Warhol had become interested in making films, more than likely inspired by the increasingly popular (and significantly gay-themed) "underground" films of Jack Smith and Kenneth Anger, but also by a nostalgic love for Hollywood and all that it encompassed. Having already canonized Elizabeth Taylor, Marilyn Monroe and Elvis Presley on canvas, Warhol invented the concept of the "superstar," a notion that essentially co-opted Hollywood's celebrity-making monopoly by suggesting that the ability to bequeath stardom rested with whoever held the camera. Warhol shot roll after roll of "screen tests," proving that everyone from the authentic upper-class to the denizens of New York's drug and drag cultures (even the biggest star of them all (www.youtube.com/watch?v=7idi_5IaMrk ) could be famous - at least until the film ran out.

Warhol's "I am a camera" facade reached its zenith in 1966 with "The Chelsea Girls," (www.youtube.com/watch?v=R6yBhWLnvR0&feature=related ) where several reels of unrelated footage were forced together into an episodic split-screen format that somehow went beyond simple voyeurism to create a composite image of New York's post-beat Underground at its best and worst. In some ways, it's a microcosm of everything in Warhol's films, from the grandstanding performances of Ondine and other street personalities to the vague sense of emptiness and dread that marks Nico's sequence. The minor success of "Chelsea Girls" justified every pronouncement Warhol had made about celebrity and his superstars, but it also confused him and led him astray, encouraging him into less-organized and unfinishable projects like "* * * *," a 24-hour-long multi-screen experiment that alienated even the most enthusiastic underground patrons.

By 1968, Warhol had already begun to lose interest in making films, letting Paul Morrissey take over most of the film direction, mostly exploring close-but-not-quite-pornographic situations in films like "My Hustler" and "I, a Man." He continued to entertain the role of underground mogul, even starting his own film journal "Interview," but actually began a slow withdrawal from the medium. Whatever he had tried to accomplish with his films (which in later years he routinely dismissed as "boring"), his life as a filmmaker was just one of the many casualties of his 1968 shooting.

Warhol lived on for 19 more years after Solanas' attack (he died in 1987, the result of botched gallbladder surgery), but like most earlier Warhol biographers, Scherman and Dalton dismiss his late years, wrapping them up in a brief epilogue that can be summed up as follows: The '60s were over, Warhol's art was out of fashion, and he spent too much time at Studio 54 and in the company of the very rich.

The more I read about Warhol, the more I'm convinced that this casual negation of his final years is both patronizing and misleading. If Warhol's greatest achievement of the 1960s was the creation of Pop Art and its embrace of mass production, his role in shaping our understanding of celebrity and publicity, primarily through his films, was a close second, as this latest biography attests.

Warhol continued to experiment with themes of commercialisation and fame for the rest of his life, but the medium he chose to work with was himself. Twenty years after his death, as "celebrity" artists still manufacture themselves (Jeff Koons is one example, but so is the "Painter of Light" Thomas Kinkade) and non-celebrity "superstars" dominate the gossip columns (too many to list, but certainly anyone who ever appeared on a reality show counts), Warhol's legacy - 15 minutes times infinity - is a work in progress.