A great work of literature doesn't usually translate into a great movie. The language of cinema relies on externals as seen through the eye of a camera. It's a far cry from the written word, which tends to be more internal and malleable to the interpretations of the reader.

That difference is one reason why Stephen King books, with their strength being plot instead of prose, usually make for terrific movies. Faulkner, Vonnegut and Updike? "” Not so much. And that brings us to "The Road," the film version of Cormac McCarthy's 2006 novel set in post-apocalyptic America.

Bleak in subject and tone, that Pulitzer-winning, Oprah-approved work soars on McCarthy's starkly elegant writing. It is imbued with a depth perhaps impossible to replicate on celluloid without a filmmaker adopting an approach unique to the possibilities of cinema.

But director John Hillcoat ("The Proposition") foregoes that challenge by being overly faithful. It's a bit of a paradox, but "The Road" loses its way by sticking to the map of its source material.

CATASTROPHE
Welcome to the end of the world, where an unexplained catastrophe has sent the planet into its final gasps. In this ashen-gray existence, an unnamed man (Viggo Mortensen, "Eastern Promises") and his young boy (Kodi Smit-McPhee, "Romulus, My Father") head south in hopes of enduring a less brutal winter. The journey is treacherous. Food is scarce, but creepy "Mad Max"-styled cannibals are plentiful. Father and son forge ahead with the sole aim being to live, but even that edict is tenuous. The man keeps a pistol with two bullets in the chamber "” just in case.

Hillcoat and cinematographer Javier Aguirresarobe ("The Twilight Saga: New Moon") deftly reflect the book's moribund tone. They sap the world of color; the only visual warmth comes in flashbacks when the man remembers his wife (Charlize Theron, "Hancock"), who evidently checked out while the getting was good.

The film's nightmare scenario is ill-served by its episodic structure. The man and boy go here; they go there. They find an unopened can of Coca-Cola, meet an old codger (an unrecognizable Robert Duvall, "Four Christmases") and stumble upon a chamber of horrors in the middle of nowhere. While an underlying sense of menace permeates "The Road," it is hobbled by a lack of forward momentum.

The story lurches along like the man's rickety cart. Its dramatic stasis is baffling, really, but you get the impression that Hillcoat and screenwriter Joe Penhall allowed mood to trump everything else. Their few attempts to juice up dramatic tension —” voiceover narration, a cheesy music score — feel out of place.

Despite such miscalculations, "The Road" has moments of stripped-down poignancy. It is most effective capturing the unconditional love between parent and child:” the man's selfless devotion to the boy, and the boy's efforts to preserve his father's guarded compassion.

Mortensen is remarkable. Gaunt and with sunken cheeks, he is wholly convincing as someone who has lived through hell and will do anything in his power to spare his child. It is a great performance, albeit one tempered by a movie that falls short of expectations. —Phil Bacharach