It may not make complete sense to review these two films simultaneously, but I'm going to give it a shot anyway, partly because they are both new takes on old tropes… and partly because I'm really lazy.
I saw "Daybreakers" first, and went in with only a one sentence description from some magazine. I hadn't even seen the trailer, but I was intrigued nonetheless. In the film, it's ten years since an unexplained plague began transforming people into vampires. The vampires promptly took over the world, gave everyone the chance to change, and those that didn't were rounded up and put into uber-creepy blood banks. Ethan Hawke plays a vampire hematologist working on a blood substitute, since the supplies of the real article are running low. Worse still, if you don't have a consistent supply of human blood, you basically turn into a feral bat-creature. So, the vampires are nearing their own catastrophe.
Enter Willem Dafoe as a human who managed (through a bizarre coincidence) to become a vampire for about three seconds, and then be cured. He and Hawke work together to come up with a way to replicate the process, to reverse vampirism completely.
I liked the stylized look of the film, and the little details that tell us about vampire life: the houses with retractable windows, the subwalk system under the city, the stand selling coffee "still with 20% blood!" The mechanics of the ending are important, but I won't give them away. Coming up with a satisfying ending when the world is so ridiculously screwed up wasn't easy to do. It's neither easy nor sure-fire, but it's modestly hopeful, while at the same time being about as bloody as any film I've ever seen.
"The Book of Eli" is another film with a very familiar premise: the world was destroyed in some cataclysmic (probably nuclear) war, and Denzel Washington is a mysterious "walker" with a precious book. Gary Oldman is the town boss (somewhere in the extra-blasted southwest) who really, really wants that book.
The ads were somewhat cagey about what the book was, but the film doesn't take long to make it clear that the book in question is The Bible. Washington wants to get it into the hands of someone who will use the book for good. Oldman wants to use it to take over… well, pretty much everything. It's an interesting tightrope the film walks between the positive use of faith, and the horrifying power of religion as a tool of mass control. I suspect that balance is the only reason a film about religion could get made. (Outside the "Christian" media, I mean.)
I enjoyed the film, partly because the story had very few real holes in it. (Could people really have destroyed almost all the Bibles in the world?) Most important, the film looked amazing. The scenes of past destruction were affecting without being maudlin or overdone. And the performances were good. Denzel has rarely been so selflessly heroic. Or so scruffy.