It seems somehow wrong that Alex Gibney’s “Gonzo: The Life and Work of Dr. Hunter S. Thompson” will probably do better business than the director’s previous film, “Taxi to the Dark Side,” the Academy Award-winning documentary about torture and war. Unlike the cogent, illuminating synthesis accomplished in that film, “Gonzo” presents, with little insight, a passable greatest-hits parade about the legendary drug-enhanced journalist who probed the considerable dark side of his era.

“Gonzo” essentially unfolds as a daisy-chain chronicle of Thompson’s exploits from the late 1960s through the mid-’70s, shadowed by his subsequent comedown, which finally concluded in 2005 with his suicide at age 67. The Louisville-born freelancer-in-full made his first big stirs with a finely observed 1966 report on the Hell’s Angels motorcycle gang, and a proto-gonzo missive from the Kentucky Derby in 1970. After an inspired run for sheriff of Pitkin County, Colo. (on what he and his backers dubbed the “freak power” ticket), he hit his stride with his iconic “Fear and Loathing” pieces for Rolling Stone.

That coverage, from the 1972 campaign trail, sealed the Thompson legend. His first-person reporting mingled self-dramatization, hard truths, media savvy, and mood-altering embellishment. “Gonzo,” flush with archival footage and big-name players, alternately crows over and wonders at his disdain for President Nixon and Vice President Humphrey, his fabulism about the ill-fated senator from Maine, Edward Muskie, his friendship with the English illustrator Ralph Steadman, his idealistic longings for George McGovern, his “discovery” of Jimmy Carter, and so on.

“Gonzo,” which opens in the city on Friday following an extensive run on the festival circuit, also devotes time to Thompson’s wives, Rolling Stone editor Jann Werner, and others who testify to his reckless approach to personal upkeep and deadlines. And political figures with firsthand experience — including Nixon campaign manager Pat Buchanan, Mr. McGovern and his campaign manager, Gary Hart, and President Carter — pay tempered respects. Fellow Kentuckian Johnny Depp, who played Thompson in Terry Gilliam’s 1998 adaptation of “Fear and Loathing in Las Vegas” and palled around with the writer in his spare time, turns up, repeatedly, to intone excerpts of Thompson’s prose, wave a gun around, and incidentally demonstrate Thompson’s enduring appeal among his tiresome admirers.

But despite its resources and “Behind the Music” fade-out, “Gonzo” doesn’t truly dig past Thompson’s familiar mythos. This is a common shortcoming among biographical documentaries (if not, ordinarily, Mr. Gibney’s), but the two-hour chronicle that is “Gonzo” is especially disappointing because, well, no one told stories about Hunter S. Thompson better than Hunter S. Thompson, who did so in the course of crafting genuine insights about his putative subject matter.

The writer Tom Wolfe, who helped lead the New Journalism movement in the early ’70s partly from Thompson’s example, suggests a literary lineage with Mark Twain, and Mr. Hart bravely attaches an “infantile” aspect to Thompson. Still, a real reckoning with the writer-adventurer is missing. “Gonzo” leaves intact but does not adequately probe his status as someone uncomfortably between hero and mascot, a veteran of a bygone zeitgeist, forever wearing his fishing hat and aviator shades. And Mr. Depp, who last appeared in a documentary half-clad in pirate’s garb (“Joe Strummer: The Future Is Unwritten”), should not be our gatekeeper to the man’s writings.

“Gonzo” makes some mention of the fear and loathing of our own time, partly because Thompson was still around to write about it (he referred to President Bush as “the goofy Child President”) before he shot himself in his home. But even if Mr. Gibney makes a few rudimentary synaptic connections, his documentary as a whole is further undermined by some imprudent stylistic choices, including a head-clutchingly hackneyed ’60s soundtrack and ill-advised flourishes such as the pointless rear-projection used in interviews with Thompson’s wife and a reimagining of a moment from Thompson’s Hell’s Angels book.

The path from the alarmingly innocent, consternated-schoolboy face we see in the ’60s to the husky recluse of the film’s end, aware of better days but pecking away, remains tantalizing. At least, with “Gonzo,” Thompson, whose explosive preplanned funeral concludes the film, will be reintroduced to a younger generation that perhaps was weaned on his 21st-century column for ESPN.com. And a commercially successful “Gonzo” might be some comfort to Mr. Gibney, who was last reported to be suing over the box-office whimpers of “Taxi to the Dark Side.”