The Book of Eli has the potential to be a great film or complete rubbish depending on your expectations of what is to come. If you are looking for a film with some deeper meaning then I would not recommend it. However, if you are looking for a film with beautiful cinematography, solid acting and a little bit of fun action then you will be pleased.
The key in watching the film is to not buy into the plot too much, which is where the viewer is going to be disappointed. The ending is a little far fetched and I couldn't help but roll my eyes. Although I honestly don't see a particularly good ending for the basic premise of the film.
If you are able to put the silliness with the story behind you, the film is wonderfully done. There is great camera work with interesting angles and framing; the set showcases the contrast between the stark light of the sun and the shadows where humankind is hiding; and the acting makes you want to buy into the characters and their conflicts.
I would recommend seeing the film, just don't get too involved with the story. Instead concentrate on the acting and the scene.