I DOUBT any book means more to a single professional sect than Fear and Loathing on the Campaign Trail ’72 means to political journalists.

It’s been read and reread by practically every living reporter, and you can still spot the familiar red (it was red back then) cover of Fear and Loathing ’72 poking out of the duffel bags of the reporters sent to follow the likes of Mitt Romney, Rick Santorum, and Barack Obama on the journalistic Siberia known as the Campaign Trail.

Decades after it was written, in fact, Fear and Loathing ’72 is still considered a kind of bible of political reporting. It’s given birth to a whole generation of clichés and literary memes, with many campaign reporters (including, unfortunately, me) finding themselves consciously or unconsciously making villainous Nixons, or Quislingian Muskies, or Christlike McGoverns out of each new quadrennial batch of presidential pretenders. Even the process itself has evolved to keep pace with the narrative expectations for the campaign story we all have now because of Hunter and Fear and Loathing.

The scenes in this book where Hunter shoots zingers at beered-up McGovern staffers at places like “a party on the roof of the Doral” might have just been stylised asides in the book, but on the real Campaign Trail they’ve become formalised parts of the messaging process, where both reporters and candidates constantly use these Thompsonian backdrops as vehicles to move their respective products.

Every campaign seems to have a hotshot reporter and a campaign manager who recreate and replay the roles of Hunter and Frank Mankiewicz (Karl Rove has played the part a few times), and if this or that campaign’s staffers don’t come down to the hotel bar often enough for the chummy late-night off-the-record bull sessions that became campaign legend because of this book, reporters will complain out loud, like the failure to follow the script is a character flaw of the candidate.

That this is a great piece of documentary journalism about how American politics works is beyond question — for as long as people are interested in the topic, this will be one of the first places people look to find out what the US electoral process looks like and smells like and sounds like, off-camera.

Thompson caught countless nuances of that particular race that probably eluded the rest of the established reporters. It shines through in the book that he was not merely interested in the 1972 campaign but obsessed by it, and he followed the minutiae of it with an addict’s tenacity. For instance, there’s a scene early in the book when he confronts McGovern’s New Hampshire campaign manager, Joe Granmaison, badgering the portly pol about having been a Johnson delegate in 1968:

“Let’s talk about that word accountable,” I said. “I get the feeling you stepped in shit on that one.”

“What do you mean?” he snapped. “Just because I was a Johnson delegate doesn’t mean anything. I’m not running for anything.”

Now, not many reporters would bother to find out what a lowly regional manager for a primary long-shot candidate was doing four years ago, but Hunter had to know. The book reeked of a kind of desperation to know where everyone he met stood on the manic quest to find meaning and redemption that was his campaign adventure.

The obsession made for great theatre, but it also produced great journalism. Hunter knew the geography of the 1972 campaign the way a stalker knows a starlet’s travel routine, and when he put it all down on paper, it was lit up with the kind of vivid detail that only a genuinely crazy person, all mixed up with rage and misplaced love, can bring to a subject.

Hunter had such a brilliantly flashy narrative style that a lot of people were fooled into thinking that’s all he was — a wacky, drug-addled literary party animal with a gift for memorable insults and profanity-laden one-liners. The people who understood him the least had this idea that he was just the journalistic version of a rock star, an abject hedonist with a gift for the catchy tune who was popular with kids because he stood for Letting Loose and Getting Off without consequence.

People all over the world don’t identify with Hunter Thompson because he was some kind of all-world fraternity-party God who made a sexy living mainlining human adrenal fluids and spray-painting obscenities on the sides of racing yachts. No, they connect with the deathly earnest, passionate, troubled person underneath, the one who was so bothered by the various unanswerable issues of life that he went overboard trying to medicate the questions away.

This book buzzes with genuine surprise and outrage that people could swallow wholesale bogus marketing formulations like “the ideal centrist candidate”, or could pull a lever for Nixon, a “Barbie-Doll president, with his box-full of Barbie Doll children”.

When I read this book now, it reminds me a lot more of vast comic epics like The Castle or The Trial than one of Fear and Loathing’s smart nonfiction thematic contemporaries (like the excellent The Selling of the President 1968, for instance). Just like Kafka’s Land Surveyor, Hunter in Campaign Trail ’72 enters a nightmarish maze of deceptions and prevarications and proceeds to throw open every door — bursting into every room with a circus clown’s theatrical self-importance and impeccably bad timing — searching every nook and cranny for the great Answer, for Justice.

What makes the story so painful, and so painfully funny, is that Hunter chooses the presidential campaign, of all places, to conduct this hopeless search for truth and justice. It’s probably worse now than it was in Hunter’s day, but the American presidential campaign is the last place in the world a sane man would go in search of anything like honesty. It may be the most fake place on earth.

Both now and in Thompson’s day, most of the press figures we lionise as great pundits and commentators seem to think it’s proper to mute our expectations for public figures. We’re constantly told that politicians should be given credit for being “realistic” (really code for “being willing to sell out your constituents in order to get elected”) and that demanding “purity” from our leaders is somehow immature (Hillary Clinton had to vote for the Iraq war; otherwise she would have ruined her presidential chances!).

To me, the reason so many pundits and politicians take this stance is because the alternative is so painful: If you cling to hope and belief, the distance between the ideal and the corrupt reality is so great, it’s just too much for most normal people to handle. So they make peace with the lie, rather than drive themselves crazy worrying about how horrible and ridiculous things really are.

But Thompson never made that calculation. He never stooped to trying to sell us on stupidities about “electability” and “realism”. Instead, he stared right into the flaming-hot sun of shameless lies and cynical horseshit that is our politics, and he described exactly what he saw — probably at serious cost to his own mental health, but the benefit to us was Fear and Loathing on the Campaign Trail ’72.

We can easily imagine how Hunter would have described people like Mitt Romney (I’m guessing he would have reached for “depraved scumsucking whore” pretty early in his coverage) and Rick Santorum (“screeching rectum-faced celibate”?).

But more than anything, this book remains fresh because Thompson’s writing style hasn’t aged a single day since 1972.

On top of everything else, on top of all the passion and the illuminating outrage and the great journalism, the guy was just one of a kind as a writer. Nobody was ever more fun to read. He’s the best there ever was, and still the best there is.

* Excerpted from Matt Taibbi’s introduction to the 40th anniversary edition of Hunter S Thompson’s Fear and Loathing on the Campaign Trail ’72, (Simon & Schuster)