Saw the movie, and liked it quite well. Thought Will did a dang good job of carrying the movie singlehandedly through almost all of it (Well, him and the dog.)
Picked up the book shortly thereafter, and was blown away! The author's name is Richard Matheson, and Stephen King lists him as a major influence - and there's a good reason for this! With the reading of that one book (Had "I am Legend" and a few more short stories - a few of which had also been made into movies!) He has moved up into the top of my list of favorite authors!