I haven't started reading I am Legend, yet. But I will, oh, I will. Fran's comments yesterday got me thinking about reading a book vs. watching a movie. I'm a reader. Always have been. I enjoy movies as well, although these days, I don't go to the theaters as often as I used to. DVD's in the living room are more my speed. (with some kind of craft, preferably.)
My problem with movies is this: you have to leave to much out of the book to fit it into 90 minutes. Even when the movie is wonderful, they have just left out so much. Parts that I loved! Parts that I wanted to see! So, if I read the book before I see the movie, generally I'm disappointed in the movie at some level. Now there is a way around that, sort of. If I see a movie today for a book that I read 20 years ago, then I'm OK. I don't remember every detail of the book and I can enjoy what they put into the movie. The Lord of the Rings Trilogy of movies was like that. I know they could not possibly include all the richness of detail that JRR Tolkien included in his books. There is just too much. No, really, too much.
So, my general preference is to watch a movie first, then read the book. I enjoy the addition of the character's thoughts, the additional scenes, and what have you. I feel my experience with the story has been enriched instead of robbed. Still, there was an exception to this "rule" as well. I read the book for the original Star Wars, by George Lucas, and it was pretty much word for word with the movie. I felt cheated! I wanted the extra, and I was really disappointed. I haven't read any other Star Wars Universe book. That's how disappointed I was. (ask me how many Star Trek books I own, on the other hand, and my geek will begin to show again.) Anyway, I'm looking forward to reading I am Legend, even though it may be some time next year before I can get to it.