Grade: B

Hunter S. Thompson was a thoroughly unconventional journalist, an outsized personality with an exorbitantly flamboyant style and a seemingly insatiable appetite for (and tolerance of) drugs and alcohol of every sort. Trying to capture him on film is a daunting task. Art Linson’s torturous “Where the Buffalo Roam” (1980), with Bill Murray, was a total misfire, and Terry Gilliam’s wild-eyed attempt, in “Fear and Loathing in Las Vegas” (1998), was an almost unmitigated disaster, despite Johnny Depp’s uninhibited lead performance. This documentary portrait by Alex Gibney is much more successful. “Gonzo,” the word that was taken up to identify the deliberately outrageous, highly subjective reportage that Thompson practiced, is more florid in approach than most documentaries, but not by all that much—it certainly doesn’t go in for all the visual excesses that Gilliam allowed himself. So in that respect it hardly can be said to match the woozy brilliance of its subject and his writing. But in its fairly straightforward, but energetic way it captures a good deal of what made Thompson a unique figure.

Structurally “Gonzo” is pretty conventional. After a scene-setting preface of sorts, it goes through Thompson’s career chronologically, juxtaposing stills and archival material (film footage and audio tapes) with excerpts from interviews with family (Thompson’s two wives, Sondi and Anita, and son Juan), colleagues like Rolling Stone editor Jann Wenner and Tom Wolfe, and his biographer. It covers all the major episodes—his difficult Kentucky youth and intense desire to become a writer; the early, career-making coverage of Hell’s Angels; the muckraking coverage of the Kentucky Derby; the run for sheriff of Aspen, Colorado; his Las Vegas book and idiosyncratic political reporting in the sixties and seventies; his later years and ultimate suicide. The image that emerges is of a talented man with, as his closest friends note, a very dark side that could find expression in terrible, childish tantrums.

But the range of data that Gibney and his expert editor Alison Ellwood include—in swift, vibrant strokes that make use of split screens, quick cuts and onscreen “texting”—is much broader than that description would suggest. There are clips from Gilliam’s picture, along with substantial readings from Thompson’s writing by Depp. There are TV clips from early interviews about the Hell’s Angels coverage (with Angels honcho Sonny Barger bursting in to confront him) and even from the quiz show, “To Tell the Truth,” on which Thompson appeared and tried to fool the celebrity panel about his identity. There are recollections by politicians about whom Thompson wrote—George McGovern, Gary Hart, Jimmy Carter (whose national career he helped launch)—though understandably they tend to be those whom he treated favorably. (As counterpoint, Gibney scored a session with Nixon’s man Pat Buchanan, which yields one of the film’s best moments, when a motorcycle appropriately roars by outside just as Buchanan is finishing his remarks.) And while Gary Trudeau may be missing, his creation Duke—who became, as Thompson apparently felt, more real to many than he was toward the close—is present, too. The musical choices are apt as well.

“Gonzo” might be thought a peculiar project for Gibney, who won the Oscar last year for the lacerating “Taxi to the Dark Side,” which took on the subject of American abuse of prisoners in the so-called war on terror. But in a way it’s of a piece with the earlier film. “Taxi” was essentially an assault on the misdeeds of the military establishment and their civilian masters, and here Gibney attempts to recapture the spirit of a writer who took on the powers that be forty years ago. Happily the director’s enthusiasm for his subject proves infectious, and though the film can’t explain Thompson in full, it gets more of him on film than any previous attempt—including the follies of Linson and Gilliam. It’s revealing, honest and—most of all—genuinely engaging.