Laughter rolls in from the hotel corridor as Joel and Ethan Coen approach. Off-duty and off-guard, the fraternal duo behind many of the finest American films of the past 25 years are natural jokers, as wordy and witty as one of their absurdist comedies. But with the interview microphone on they instantly adopt their expression of blank bemusement. The brothers grim, getting into character for another of their trademark Zen minimalist antiinterviews.

The rules of Coens interviews are well established. Most of my questions will meet with cordial evasions and disingenuous deflections. Joel, the older brother at 53, will be gnomic, taciturn and bone-dry. Ethan, three years his junior, will be more giggly and effusive, but just as resistant to critical probing.

The deadpan duo’s latest film, No Country for Old Men, arrives trailing critical prizes and Oscar buzz. Faithfully adapted from Cormac McCarthy’s novel, this exacting and remorselessly bleak thriller is a masterclass in brooding minimalism and bruise-black humour that is already drawing parallels with their debut Blood Simple (1984) and the Oscar-winning Fargo (1996).

Naturally, the brothers shrug off these comparisons. “I guess, in tone, it’s more like those than our other movies,” Joel concedes grudgingly. “The similarities with Fargo occurred to us, but only retrospectively. They weren’t there when we first read the book.”

Set 30 years ago in the lonely desert badlands of West Texas, No Country for Old Men is a Sam Peckinpah-style neo-western starring Josh Brolin as a down-at-heel handyman who steals the proceeds of a botched drug deal. Javier Bardem plays the psychotic hit man on his trail, and Tommy Lee Jones the ageing local sheriff appalled by the carnage opening up around him. Most Coen films feature violent and untimely death, but the savagery is more pronounced this time.

“We don’t have any rules about how we depict violence, or how much violence is in a movie,” Joel explains. “It’s a calibration on a case-by-case basis.”

Ethan describes the Coens’ attitude to carnage as “almost like a design question – like how much red is too much red in this set?”

It is this sort of detached, egghead response that critics point to as proof that the brothers make films purely as an arid intellectual exercise. Do they never consider the ethics of presenting violence onscreen? “No, it’s all within the context of the story,” Joel says. “Although certainly you are aware that it has power.”

The dark heart of No Country for Old Men is Bardem’s underworld executioner Chigurh, a cold-blooded killing machine clearly motivated by something deeper than pride in his work. It is a chilling performance, but also disturbingly funny – a very Coen combination.

“They are among the few directors able to mix the most weird situations and characters with the funniest moments,” Bardem says. “So you feel engaged by those people and at the same time you are repulsed.”

With its Texan cowboy imagery and its dramatic themes of violence and retribution, No Country for Old Mencould also be read as an oblique commentary on Bush-era America. But not, of course, by the Coens.

“I don’t think the book was topical or about political things,” Ethan says. “That’s not something we think about when we do a movie or write a story,” Joel shrugs.

“There’s not a lot of great messages in their films,” insists George Clooney, a regular Coens collaborator. “Joel and Ethan don’t really set out to teach anything, that’s what I love about them. They’re just irreverent. They have fun.”

The Coens are closing in on their first quarter of a century in cinema. Years before Quentin Tarantino or Steven Soderbergh made their reputations, these brothers grim were reinventing pulp genres with high-brow movie in-jokes and ironic violence. Despite their high critical standing, they have scored only a handful of box-office hits, notably Barton Fink, Fargo and O Brother Where Art Thou? And yet they continue to enjoy an enviable amount of creative autonomy and industry clout. They write, direct, produce and edit their own films.

Based in New York, the Coens still operate as a tight-knit family, keeping Hollywood at a distance. Joel has been married to regular leading lady Frances McDormand since 1984. Ethan married Tricia Cooke, an editor on several Coen features, in 1993. Both are fathers.

Remarkably, the duo’s personal and professional relationship has endured. No friction, no fights? “We frequently get asked that,” Ethan frowns. “I guess it’s inevitable, because we’re siblings. But no. No more than we do with any of the other people we collaborate with.”

However No Country for Old Men performs at the box-office, they have already completed their next project, which is due for release this year. Starring Clooney and McDormand alongside Brad Pitt and John Malkovich, Burn After Reading is a politically slanted farce set in contemporary Washington. “It’s about a CIA analyst and someone who manages a gym in Washington,” Ethan explains. “Hilarity ensues.”

It sounds as if it could potentially address serious contemporary issues. Except, of course, that the Coens don’t make political statements. And even if they did, I suggest, they would still deny it was political. Or a statement. Ethan snickers: “The characters are resolutely smaller than life. They can’t be made to stand in for any large social or political considerations, or anything sounding important. They are unrelentingly unimportant.”

Naturally. But then, of course, he would say that.

— No Country for Old Men opens on Jan 18

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