I know it sounds like a bunch of cliches but this book gripped me so much I couldn't put it down and read it in just a few hours. A sometimes bleak study of the human condition it is also engrossing, thought-provoking and moving. It is also one of the few "horror" novels out of hundreds I have read that have genuinely scared me.
Basically it is the story of Robert Neville, the lone survivor of a plague that sends its victims into a coma, followed eventually by death and vampirism. By day Neville hunts sleeping plague victims and vampires and disposes of them in the traditional manner. By night he locks himself away while hordes of vampires attack his well-defended house. Eventually he seeks scientific explanations for the causes of vampirism and tries to find a cure. In that respect I think the story must have been an influence on the Blade comics and movies (just don't expect hi-tech weapons, martial arts and cool shades!!).
As Neville becomes more resigned to his situation, and gradually gets used to the nightly attacks of vampires on his well-defended house, so does the reader. The vampires become almost incidental and the writing focusses more on Neville's thoughts and preoccupations. Until, that is, Neville loses track of time and gets caught outside, miles from home at nightfall. It is a testament to Matheson's writing that at this point the thought of being in Neville's position and having to run the gauntlet of vampires waiting for him outside his only safe haven is truly terrifying!
The pseudo-scientific explanations for the characteristics of vampirism seem a little silly, especially the "body glue", but these are really incidental to the story, as is the futuristic 1970's setting, and you shouldn't let these put you off.
I would recommend this book to anyone.