CHANCES are that you already know aboutTheBig Lebowski, or maybe not. Withits unique combinationof nihilists, marmots and severed toes, the movie was always expected to be a big deal.

In 1998, the Coen brothers had just won two Oscars for their previous film, Fargo. The Lebowski cast included Jeff Bridges, John Goodman and Julianne Moore. With nods to The Big Sleep and The Long Goodbye, the comedy-meets-film-noir script was tight: a case of mistaken identity, wrapped in razor-sharp dialogue, set in suburban Los Angeles at the start of the first Gulf War.

It bombed. In its opening weekend, the film took just $5 million at the US box office. In the weeks to follow, on global release, it barely recouped its budget of $15 million. But almost a decade and 20 million DVD sales later, the flame is still steadily burning.

WhentheLebowskiFeststartedin Louisville, Kentucky in 2002, it was a low-key affair: 150 people showed up from various states, unsure what to expect, but drawn together by a common cause. Like Jeff Bridges' character The Dude, they bowled and drank White Russians, before settling down to watch the film. The following year was much the same.

The formula has changed little since, but the numbers and venues keep growing. No longer content to go unnamed, die-hard fans now refer to themselves as Achievers, a sobriquet lifted from the Little Lebowski UrbanAchieversofthefilm.Andnext month they're coming to Scotland.

"We're so excited about hearing the dialogue quoted in a Scottish accent and seeing whatScottishAchieversarelike,"says Lebowski Fest founder Will Russell. On the pressreleasetohisnewbook,I'mA Lebowski, You're A Lebowski, he describes himself as a magician. In reality, he sells T-shirts designed by local artists in Kentucky.

The story goes that he was at a tattoo convention with a friend, quoting lines from the film, as they had done a million times before. "The people at the next booth started joining in and we realised we were not alone with our obsession," he recalls. "We had an enormous sense of bonding over The Big Lebowski and the idea for the festival was born."

Russell speaks in "umms" and "awws" but is articulate about his heroes. "I think a big part of the film's appeal is definitely The Dude,"hesays."He'snotinterestedin materialism or the rat race. He just wants to go bowling, take bubble-baths and help a lady-friend conceive."

Of course, in the film, none of this happens for The Dude without conflict. From the moment he is mistaken by thugs for an ageing millionaire, who is also called Jeff Lebowski, things go from bad to unbearable. Hired to investigate a bogus kidnapping, The Dude endures the brunt of the film's violence, and is present in every scene but one.

Casting Jeff Bridges as a hard-boiled detective in the body of a laid-back hippy may have seemed like a risk. But pairing The Dude with his Vietnam war veteran bowling buddy Walter Sobchak (John Goodman) and a nearly non-speaking Steve Buscemi somehow worked, earning the film and its characters an unlikely iconic status. Bridges, in his foreword to I'm A Lebowski, says he would be "delighted" if the role he was most remembered for was The Dude.

Russell, for his part, is in flux. "I definitely like to take it easy, ride my bike around town and listen to my headphones, and that's The Dude in me. Then there's the Walter in me that gives a shit about the rules. I'm in charge of organising the festival itinerary, which is a very un-Dude thing to do."

Non-Dudes at the festival typically come in the guise of other Lebowski characters, whether it's Maude Lebowski, the affected feminist painter, or the film's cowboy narrator, the Stranger, played by Sam Elliot. The more ambitious come dressed as props, cultural references or even lines of dialogue.

"Last year we had someone dressed as a world of pain' one of Walter's bellowed threats," says Russell. "He had built a giant globe that he walked around in all night. Someone else brought his uncle's ashes in a can and entered him in the costume contest as Donny. He won second place."

Scott Shuffitt, fellow festival founder and co-author of I'm A Lebowski, identifies closely with The Dude, and lives a "strikes and gutters" life. He doesn't watch the film as much as he used to, but only because his wife is sick of him apeing every line. "Lebowski has become a bigger part of my life than I could ever have imagined," he says. "Being able to talk about it all the time and experience it with other people is such a wonderful thing."

He gives many reasons for the film's enduring hold on him, of which these are just a few: "It's hilarious, first and foremost. The Coen Brothers wrote it really well and it's just so visually pleasing. The sun is shining most of the time and there are so many great shots of California."

Shuffitt and his friends aren't the only Lebowski acolytes. The internet-based Church Of The Latter-Day Dude takes appreciation of the film to new heights. Not content simply to dress down and smoke Thai stick, American freelance journalist Oliver Benjamin ordains "Dudeist" ministers online and plumbs The Big Lebowski for spiritual meaning.

"The more you see the film, the more you see its connections and congruencies with philosophy and religious literature," he says. There's the copy of John Paul Sartre's Being And Nothingness on The Dude's nightstand, for example; and the fact he writes a prophetic cheque at the start of the film dated September 11, 1991.

Benjamin runs his church from a small town in northern Thailand, which he says is "suited to the Dudeist philosophy", and from where he publishes his regular Tao Of The Dude column.

"Themostimportantthingabout Dudeism is that you're not supposed to tell other people what to do," he says. "Though The Dude lives in Los Angeles, which is not a very natural place, he's very much in harmony with his surroundings. He's basically a modern Taoist philosopher, inadvertently, and without being pretentious about it. In a conflicted world, where bad things happen, people find The Dude really inspiring."

But like most religions, there are some who have been airbrushed out. No mention is made in Benjamin's philosophy of the film's hip-swivelling pederast, The Jesus, played by John Turturro, nor the porn star-turned-nihilist Karl Hungus, played by Peter Stromare. And, like most faiths, The Big Lebowski has its share of non-believers.

"It's one of the Coen Brothers' films I really hate," says Shane Danielsen, film historian and former head of the Edinburgh International Film Festival. "I can't fathom why, but it just rubs me up the wrong way." He remembers seeing Lebowski on its original release, sitting stony-faced while friends around him laughed. Despite repeat viewings, and an appreciation for the film's craft, he has concerns.

Like the Stranger, who complains about all the "cussing" in the script, Danielsen thinks his ire might boil down to the F-word and its variations, repeated 281 times during the film. "The profanity is incessant and actually works against the comic rhythms the Coen Brothers wanted," he says. "To me, The Dude is an emblem of the fallen world, far removed from the elegance of the screwball comedies the Coens wanted to emulate."

It is, as The Dude might put it, just an opinion, man, and not one that is likely to sway the faithful. For them, the film's many mysteries, and the space they allow for speculation, are all-important. We never know whether The Dude wins his bowling competition, though we know before he does that he will soon become a father. We can also assume, if this were real life, that the child would be hailed as the Messiah.

"What we're aiming for is a really great party and nothing more," says Russell. "We want to get like-minded people together to drink White Russians and bowl. We're going to screen the movie in Edinburgh, we're going to have bands playing - it's going to be a real good time."

I'm A Lebowski, You're A Lebowski (Canongate, £12.99) is published tomorrow. Lebowski Fest takes place at Tenpin, Fountain Park, Edinburgh on August 24. Visit www.lebowskifest.com for more details.