Cormac McCarthy is not an easy author to adapt from page to screen.
Each of his books seems to pose a different challenge to screenwriters and directors, too, and so there's no one answer for how to crack the problem of bringing his books to the bigscreen. I think the Coens did a tremendous job with "No Country For Old Men," and there are parts of "All The Pretty Horses" that work very well, even if the film as a whole is sort of a heavily-manhandled mess as it was released.
"The Road" was a very different type of challenge, and it's one that I'm not sure John Hillcoat mastered. He makes a valiant attempt, but the ways the film frustrated me as a viewer suggest that the job just plain got away from him, and as an end result, I think the film is muted, half-hearted, and dissatisfying, and one of the year's big heartbreaks, all things considered.
There is, after all, a long and healthy tradition of post-apocalyptic cinema, some of it trashy, some of it more serious-minded, and there are certainly classics in the genre that are hard to beat. For "The Road" to stand apart from what's come before, it needed to find a particular angle on the material that we haven't seen before, or contribute something new to the language of how the ruined world might be portrayed on film. The dirty secret of McCarthy's justly-acclaimed novel is that the appeal does not lie in the story being told, but in how that story is told. It's not what happens... it's the way McCarthy tells it. "The Road" is all about language, about the evocative nature of how McCarthy paints his picture, and the spare emotional detail. It's a powerhouse of a book, but it's not especially a powerhouse of a story.