My favorite book is I am Legend by Richard Matheson.
I read it a few years ago, and i love it. It was written very nicely and has an amazing story. I can't really remember exactly why I like it so much though xP
Also, it's extremely different from the movie.
The description on the back says:
"Robert Neville is the last man on Earth... but he is not alone.
Every other man, woman, and child on Earth has become a vampire,
and they are hungry for Neville's blood.
By day, he is the hunter, stalking the sleeping undead through
the abandoned ruins of civilization. By night, he barricades himself
in his home and prays for the dawn.
How long can one man survive in a world of vampires?"