In reference to my entry below, Will sez: “The Earth Abides (originally published in 1949) is probably the best SF novel out there to explore this theme. A geologist goes solo backpacking, and comes back to find almost all of humanity dead due to a sudden world-wide plague. The novel chronicles the following life of the protagonist and a small band of fellow survivors. The first few years involve the gradual failing of services such as power, water, and the highway system. Later years are more focused on the growing encroachment of wilderness on the former developed world. A highly environmental and ecologically oriented novel; unusual for its time.” Link