The story itself keeps the eye of the reader focused on Neville to keep the reader from ever even thinking about sympathizing with the vampires. The vampires themselves, being classical vampires following most of the traditional rules, do not need explaining beyond that they're there and the methods work. The focus of the story becomes Neville's desire to cure them and understand them to a scientific level and the intrigue that keeps the reader is his success on finding out why they work the way they do. It is telling of how human's first reaction to anything new is to kill it and study it, which reminds me of books or films about aliens where the human reaction is always aggressive. Neville embodies human aggression, primitive instincts, and his desire to survive which even he cannot understand.
His desire to possess and control ultimately leads to the accumulation of the dog and the vampire woman, Ruth. It is with these two characters the reader witnesses Neville's division from what or who he once was to the monster we get to see him as at the ending of the story. In retrospect, trying to visualize the story from Ruth's perspective, every action Neville took resembles a genocidal maniac or serial killer who is ruthless (ha, Ruth...Ruthless) and praying on his victims when they are of no competition to him. Although he is not gender biased on who he kills, he definitely seems more interested in the women. In speculation, the reason why the ghoulish vampires that were always dead outside of Neville's door in the morning were most likely offerings, at least it is the only way to justify why they were always women.
Matheson excellently keeps the reader sympathizing with Neville until his last few moments before execution, where Ruth reminds Neville that he has been as terrifying to them as they are to him. Neville criticizes the gang of vampires killing the ghouls savagely, but as he states they could do it while they are sleeping like he does. It plays with the subject of honor killing, killing to defend oneself, and killing just for the pleasure.
There are certainly three types of monsters presented in the story. The mindless ghouls at the beginning of the vampire evolution, the vampires who are trying to adapt to the new world from being human, and Neville, the last remaining human. Each one tackles the concept of monster in a different way. Neville is killing people he once knew because they have become rabid. He does not stop to differentiate between the ghouls or the vampires, he just assumes they are all the same. This is reminiscent of killers who take out their anger or frustrations on others who are similar. The ghouls are the literal monsters of the story. They act on pure instinct and it is that instinct that makes them a danger to the other apex predators in the story. The vampires at the end are the most identifiable. They are doing what they must to survive, and the fact that they are a classifiable monster outside of the book is the only thing that makes them monsters in the book. Otherwise, the vampires like Ruth, are the most civilized of all of the characters.
