The question about Hunter Thompson was always whether he eventually became that which he pretended to be, or whether that was the way he really was from the start.

The fitfully fascinating new documentary "Gonzo: The Life and Work of Dr. Hunter S. Thompson" comes down firmly on both sides. Which, come to think of it, is exactly how the paradox-courting Thompson would have liked it.

Simultaneously lucid and drug-addled, Thompson blazed a new form of journalism in the 1960s and'70s that made him one of the most popular cult writers in America. Although the documentary makes a good stab at beginning to unravel the enigma, it is unlikely to appeal to anyone who is unfamiliar with his writings. An appreciation of the film presupposes an appreciation of his output.

Thompson shot to widespread, but demographically limited, fame with his articles for Rolling Stone and his groundbreaking books on the Hell's Angels, the 1972 presidential campaign of George McGovern, and Las Vegas (for my money, the first two paragraphs of "Fear and Loathing in Las Vegas" rank as one of the finest openings of any American book, ever).

With a wealth of filmed archival material, "Gonzo" covers Thompson's quixotic coverage of these subjects and more. In a wide-ranging series of interviews, those who knew him reveal an affection for him as well as a fear.

"I think his story was tragic," says his first wife. "He was loving. He was generous. And on the other side of the spectrum, the boy and the man was vicious."

At which point director Alex Gibney cuts to a shocking clip of a seemingly unstable Thompson unleashing his untethered anger.

Gibney has made a name for himself as a documentarian par excellence with "Enron: The Smartest Guys in the Room" and last year's Oscar-winning "Taxi to the Dark Side." "Gonzo" is another winner, although without the controversy of those two films it comes across more as an intriguing character study.

The film shows Thompson to have been angry, filled with a love of his country and bitterly disappointed in the way it deviated from his ideal. Gary Hart, who calls him a friend, also calls him infantile for his inability to handle political reality. Though he cheated on his wives with a multitude of women, his real love was for his guns. His constant, heavy drug use was a way both of living on the edge and of rebelling against the authority that made drugs illegal.

"Hunter did everything for effect," says singer Jimmy Buffett, and we have no trouble believing him.

It helps the film greatly that Thompson's friends and acquaintances are so articulate. We hear from George McGovern and Jimmy Carter, both of whose campaigns Thompson supported subjectively in print, from Pat Buchanan - who seemed to like him despite their political differences - from family members, and from his colleagues at Rolling Stone (one former editor says "he was constantly pushing the limit of consciousness.")

Frank Mankiewicz, a former McGovern staffer, is seen calling Thompson's coverage "the most accurate and least factual account of that campaign."

Thompson might not have been able to separate fact from fiction, even in his own life - especially once the myth took over the man. "Gonzo" is intrigued by both; fact and fiction, myth and man.