The garlic
Garlic is the tool that the hero uses to fend off the undead. He uses garlic as a way to defend his home from vampire invasion, though it rarely helps, and broadly speaking, garlic is like Kryptonite to the undead. As a symbol, it is a bulb of life that fends off undead beings, so it is like a sign of the natural order. Clearly, the use of garlic is part of a motif, because the vampires and garlic go together like peanut butter and jelly. They are compatible symbols because one is an unnatural reversal of normal life (humans becoming monsters), and the other is a seemingly unimportant herb that saves Robert's life.
Loud music and alcohol
Perhaps the most legendary aspect of Robert's character is that, although he is deeply at odds with himself to survive, he celebrates his time by relishing in his freedom. He listens to loud music and drinks, showing that every day is a survival party. He doesn't enjoy the nights at all, so in the day, his full character comes to bloom, even if the alcohol makes his survival more difficult. He doesn't want to live if he can't live his way, and that hubris is easy to sympathize with.
Virginia, the undead wife
The symbol that best represents the tragedy of vampires is Virginia, Robert's wife. She represents his dilemma about vampires, because he wants to hope that there is something of his wife left in her to spare, but she continually tries to kill him until he finally bites the bullet (so to speak) and kills her. This represents his acceptance that vampires are monsters, not humans, and although he hates to take life from humanoid beings, he realizes that there is no humanity in them.
Ruth, the messenger
Another important symbol in the story is Ruth. She is a divine messenger who comes with a message and a tool: the message is unfortunate. She says the next wave of vampires is concerned with establishing a vampire government, and they are killing everything in the land, human or vampire, indiscriminately. She gives him a single cyanide pill, and although he concerns himself with whether she is human, she is clearly a signal to the reader that the story is reaching its climax. She is an archetype.
The symbols of death
The vampires are symbols of death fear, because they are undead and because they inflict death. Robert has to kill them, and in the end, the vampire wave who comes to kill indiscriminately is like the death symbol that set the novel into motion—nuclear bombs. The novel is concerned with death and judgment, and there are clearly religious death motifs, but the most important are the uses of crosses, the loud music that Robert enjoys, and the love for his dog who dies.
