What can you say about Gerry, the striking new film by Gus Van Sant that's being alternately hailed a masterpiece and reviled as pretentious nonsense? Gerry is the most off-beat and possibly off-putting cinematic mood trip of the year, one that will polarize people into thinking they've either just experienced a soaring, existential buddy flick or just waded through a pretentious and empty void as wide as the film's unending desert vistas.

As the film opens, two nameless friends (Casey Affleck, Matt Damon) who refer to each other as "Gerry," enter the desert on foot, searching for some deliberately vague destination. They chat casually, referring offhandedly to a game show and a few other mindless and trivial subjects.

As the sun goes down, they find themselves turned around and unable to find their way back to the path. At first, they show little concern. But as the sun rises and the following day turns into the next and on and on, they become increasingly despondent, desperate, withdrawn and isolated from the outside world and each other. They walk for days and miles, and it's fascinating to watch them evolve through the film from a couple of optimistic young guys to despondent, beaten-down ghosts.

We learn nothing else about them through exposition. Are they best friends? Are they brothers? Are they lovers? They have no conversations about who they are, what their relationship is or where they come from. They discuss nothing about the outside world. But as the situation becomes more foreboding, from their actions emerge their natural roles, with Damon the more physically secure leader and Affleck the quieter, softer and more sensitive.

As the film progresses, what seemed to be a buddy film becomes a fight for survival, and most of the usual clichés are sidestepped. There's no dissention between the two. The need for food and water is never discussed. Instead, the film focuses on their unending attempts to find their way out of the landscape itself, which emerges as a major character, with its foreboding, enveloping canyons and sped-up skies.

There's one humorous and inspired scene that finds Affleck stranded atop a lookout rock, and Damon carefully brainstorming how to get him down. And there's an almost moving moment when Affleck begins to cry and we start to sense that there's a real heart in the film, and real emotion beyond its aesthetic and existential musings.

Gerry is a most unusual experience. The film has no story, per se, at least not in the traditional sense. And much of it feels improvised, with story credit going to Damon, Affleck and Van Sant. At a time when most filmmakers struggle to get their story into a three-sentence pitch, Gerry can correctly be described as, "Two guys get lost in the desert. And then they get even more lost. And then, they're really lost."

And that's really all that happens. They walk together in separate worlds. And Van Sant, driving the film's experimental heart, photographs them in ways that are so assured and breathtaking as to only be described as sublime.

Cinematographer Harris Savides has created a world like none in any recent American film. There are moments in Gerry that are absolutely haunting. One comes late in the film and contains an extended walking shot, at dawn that is heartbreaking in its sense of finality and suggests the two dragging themselves reluctantly to hell or redemption.

It's a pure, beautiful aesthetic experiment that held me through its running time. The power of this film is not in the strength of its story, rather in the considerable force derived from its absolutely imposing physicality, whether it be the ominous, terrifyingly beautiful natural landscapes or the close-up, forsaken faces of its two leads. And the leads, though they're not required to do much traditional acting, exude a sense of fragility (Affleck) and strength (Damon) that is almost touching in its sense of awareness about the impending doom.

Gerry is a slow, methodical exercise, and never feels like much more than an elaborate stunt. But for a film with such an intentional disregard for formal narrative structure and character development, by the time it reaches its third act, it packs a pretty potent emotional wallop. I was surprised at how much I felt invested in both of the characters, or possibly actors, in Gerry.

Gerry is certainly not a film for everyone, but if you're looking for something that's defiantly offbeat, experimental and affecting in the sincerity of its performances and purity of its vision, its rewards are plenty.