As the definitive post-apocalyptic novel it beats Earth Abides by ten lengths and going away . . . because it doesn't abandon the spiritual aspect of the narrator's (and man's) situation.
Also, given the current occupant of the seat of the Ardship of Cambry, it has given me the opportunity to say a lot of ugly things about Rowan the Archdruid and the Litl Shining Man the Adam . . . . :-D