I really like this movie up to a point. It always felt to me that the ending was lacking in some ways, and I was never sure what. Later on I read the novel, and it turns out a bunch of the ending was different, and they cut a bunch of Sheriff Bell's monologue, among some other things. I feel the novel presents the characters in a much clearer way.
The biggest "missing dialogue" for me was when Sheriff Bell discusses his service in WW2. He says his squad was wiped out by German soldiers, and how he could hear his wounded comrades. He could have picked up the MG, and fought and died, or tried to save some, but he says he ran away and regrouped later. Importantly, though, he says he regrets leaving his squad behind most in life. And he implies he should have stayed back and kept fighting until death
It's long, but this dialogue sets up the most important part of Bell's character in contrast to Chigurh and Moss. He's a coward. A coward without purpose. The book isn't exactly critical of him, but rather just expresses the longing for that heroic purpose that Moss has or the self-assured evil that Chigurh has. Bell is nothing but a witness, a side character, and is not directly involved in anything. The book even makes this explicit: the scene where Bell goes to confront Chigurh is different in the novel. They don't fight, but it's clear Chigurh is watching him and can kill him, but doesn't. Why? Because, simply, Sheriff Bell is not really worthy of it. He wanted that kind of cosmic judgment, that moment of testing life and death to the fullest, and it was denied him.
But the movie misses all of this.. and it's unclear what role Sheriff Bell plays in the film as a result. He's the narrator, but he's kinda irrelevant because we don't learn why he foils the main characters (or rather, why the side characters and plot [the literal actions in the film] foil the main character and plot [Sheriff Bell and his regrets/lack of comprehension of the world].
Though Sheriff Bell's typical conservative lamenting of "no morals today" is pretty well deconstructed by both the novel and the film, so great kudos to them for that. Bell kinda starts getting it when he insists Chigurh isn't crazy, but it ends before he can fully realize the truths about the world that are lurking underneath his facade.
Basically what I'm saying is "No Country for Old Men" is an amazing novel (and reads really well as a Nietzschean text w.r.t. Sheriff Bell), and the movie is also good, it just fails the novel in a few ways that I think hold it back.
Sorry for the ramble.