I am Legend by Richard Matheson

Robert Neville is the last man left alive on Earth...but he is not alone. Every other man, woman and child on the planet has become a vampire. Neville spends his days scavenging for food and supplies, and hunting down the undead in their lairs in the ruins of civilisation. At night, he becomes the hunted and barricades himself in his home, waiting and praying for the dawn.
I Am Legend was one of the first, and certainly the most brilliant, fusions of horror and science fiction. Its powerful and disturbing reworking of the vampire myth has made it a classic and enduring novel that has had a profound impact on generations of writers. From Goodreads

I saw the film I am Legend (the one with Will Smith) quite a while ago but the book is very different and actually more scary. Following the life of Robert Neville the last man alive being tormented and hunted by vampires every night. At one point he sees a dog that is still normal. He spends weeks trying to become friends with this dog and then it gets infected and dies and he is devastated. I love the end of the book which is nothing like the film.

This book qualifies for: 
100 books in a year Reading Challenge 2012, 
Goodreads 2012 Reading Challenge, 
2012 Ebook Challenge,
A-Z  Book Challenge 2012,
FrightFall Read-a-Thon October 1 - 7 2012,
2012 Sci-Fi Challenge