ALEX GIBNEY'S latest documentary is decadent and depraved.The film-maker has, hitherto, been best known for serious, brow-furrowing features such as Enron: The Smartest Guys in the Room(financial meltdown) and the Oscar-winning Taxi to the Dark Side(chaos in Iraq).

After all that, Gonzo could be seen as a bit of idle, light relief. After all, how hard can it be to make an entertaining film on the drugcrazed, booze-drenched author of Fear and Loathing in Las Vegas? Raised in Kentucky, Thompson came to fame with a justifiably famous collection of articles on Oakland's Hells Angelsand went on to transform American letters with his invention of the (too often misused) concept of Gonzo Journalism. In the decade leading up to Fear and Loathingon the Campaign Trail '72, his classic study of American politics, Thompson thrilled counter-culture vultures with his unique combination of hard reporting and bad behaviour.
Decades in the wilderness then preceded his suicide in 2005. Any idiot could turn that story
into an enjoyable romp. Just round up a respectable collection of talking heads and set them loose.
It's not quite as simple as that, of course. Gibney has ploughed through the records and dug up a wealth of obscure material on the late Doctor. His appearance on the TV series What's My Lineis hilarious, and the numerous clips of an alert, shiny-headed Thompson make his later decline all the sadder.
It is, however, the contributions from friends, colleagues and enemies that really enliven the film.
Jann Wenner, the smug founder of Rolling Stone, comes across like a combination of Wall Street baron and televangelist. Jimmy Carter and George McGovern, two presidential candidates who, though enthusiastically supported by Thompson, could not be less like him in temperament, shake their heads and snigger wryly at the memory of his creative dissolution. More surprising still, an approving Pat Buchanan, former speechwriter for Richard Nixon, demonstrates that a sense of humour can unite even the fiercest of political foes. Featuring faux-beatnik readings by Johnny Depp, the film does inevitably gloss over the past 30 years to focus acutely on that productive decade, and it says, perhaps, too little about Thomson's somewhat unhappy influence on younger, lazier pop-culture writers. But Gonzo remains disreputably gripping throughout. How could it not?

Directed by Alex Gibney 15A cert, IFI, Dublin, 120 min