Matheson (the writer of I Am Legend) actually tries to demythologize the vampire by allowing his character to theorize that the germ which has just wiped out the entire popularion of the world is the same responsible for the creation of the vampire myth. So the book learns towards the scientific aspect of the vampire rather than the supernatural.

I am no fan of the vampire genre, but this is one of my favorite books. My favorite aspect of it is the idea of being the last man alive, which is a really frightening idea. That is one thing I liked about the trailer, I loved the scenes of New York over grown with plant life.