[I will blur the spoiler parts below in case somebody wants to see the movie and is sensitive about spoilers, though you could look at this first part which does not really give away any surprises.]
The premise for the story (based on my one viewing from several years ago at least!) is that the main character, “Eli” has the last existing copy of the Bible which he struggles to protect as he navigates the apocalyptic landscape. His mission is to get it delivered to a safe enclave or hidden “library” where people are working diligently to rebuild civilization and preserve such knowledge as they can from the last one. But between him and that goal, the nefarious villain (who stands out above all the other ‘run-of-the-mill’ thugs that populate the story) has learned of this bible and wants to get possession of it for himself because he perceives that it is a book of power, and that if he possesses it; it will secure his own little tribal domain of power and allow him to expand it. So much of the movie is spent following Eli on his quest, and this villain trying to thwart him.
So I see in the movie a much needed critique for the fundamentalistic outlook today that would have us believe there is something “magical” about scriptures and that those who have “correct” understanding (i.e. have properly decoded the valuable message there) now have access to some secrets of life that should give them a significant leg up over everyone else, and the eternal approval of God. While everybody else who either was not lucky enough to have it, or worse yet, fell afoul of some (probably liberal) doctrines that prevented them from correctly decoding the message there are condemned. In short: the bible is a book all about power … power that manifests itself in ways that the world would be forced to acknowledge and respect here and now.
Where the movie falls short in the end is that instead of taking the biblical message to heart for what it scandalously is: meek submission and self-sacrifice as a response to evil instead of reciprocating violence; the movie instead ends up being a vindication of the myth of redemptive violence and a yet further enshrining of this “magical book of powers” for some future civilization. In other words the message (to my memory) ends up being: “So the obviously evil villain completely misunderstands the importance of Scriptures. Duh! But now we’ll preserve these same scriptures for the later ‘good guys’ so that they can correctly decode them and have the benefit of that power.”
So the movie (rather predictably --what do we expect out of Hollywood?) misses an opportunity to show how scandalously revolutionary the real message of scriptures actually is. That evil and empire has already been defeated by a cross instead of cavalry or show of force.
[You could even look at the second blurred section above, because I still don’t reveal the main surprising developments and ending the movie has in store for the viewers. You only get my interpretation of the movie’s message.]