I read this book about two years ago. It still stands as one of the best science fiction books I have ever read. At that time SF was a new genre to me and I didn't really have the highest of hopes when I came across it. Never the less, I read the book in two days and loved it so much that I had to read it again immediately afterwards.
As a vampire-enthusiast I am always quite skeptic, when I read about new takes on the old myth. I was more than pleasantly surprised though, about Matheson's vampire-creatures; Not dumb, not weak, and often the center of the funniest parts in the book. He nails it with a bravado.
Another thing that I was amazed by, was Matheson's way of integrating science as a natural aspect of the story. A ubiquitous dimension in science fiction, but definitely a heart-catcher for me as a SF rookie.
The book appeals to me as a reader as it is written in a down-to-earth language, that makes it very easy to digest. You might not be a huge SF fan, but I think it's safe to say that "I am Legend" will entertain you no matter what.