Earth Abides (1949) by George R. Stewart
This is really one of the granddaddys of the post-apocalyptic fiction genre. Earth Abides won the International Fantasy Award in 1951, is included in Science Fiction: The 100 Best Books by David Pringle (both editions), was included in Locus Magazine's All Time Best Science Fiction Novels in 1987, and was a Prometheus Hall of Fame Finalist in 1990. It is, however, not a very well known book outside of the small post-apocalyptic science fiction community.
Isherwood Williams is a young geology graduate student who is bitten by a snake while up in the mountains. While he is alone in a small cabin recovering there is a massively virulent outbreak that pretty much kills everyone. Ish recovers and finds himself set adrift in an America bereft of humanity.
Strangely, the first section of the novel leaves the social implications of the disaster behind. The hero circumnavigates the country and for the most part rejects interaction with other survivors. He is shocked and fearful but also refreshingly pragmatic about the future.
Earth Abides is structured with several longer sections of detailed real-time divided by chapters called "quick-years" This allows us to see what happens with Ish in the beginning, 22 years later and finally near the end of his life.
This was a very interesting novel. In the majority of post-apocalyptic novels the hero often represents a link to the pre-disaster societal mores. In the 1940's and 1950's the codes of conduct for the middle class in America were the bedrock of their lives. Stewart's novel takes a detached and fairly contemporary view that our cultural structure is analogous to a physical structure like, say, a bridge or a water system. If mankinds upkeep were to suddenly be stopped then they would keep on for some period of time because of their inherent structure but ultimately will wither, crack, rust, deteriorate.
This book is a essential of the genre and I urge you to read it if you can find it.