Re: post-apocalyptic fiction?
Bladerunner is based on Do Androids Dream of Electric Sheep?. Both are works in their own right and are sufficiently different where I'd give the movie and the book close marks. I could never make it through The Stand because I think King was particularly long winded in that novel, but many people really like it. Dune is definitely on the top of my list, but is not so much post-apocalypse.
As drummist222 mentioned Orson Scott Card is a fantastic sci-fi writer, I really enjoyed the Ender's Game series and will probably take up his recommendation myself.
I would also check out the cyberpunk genre, Snow Crash, Neuromancer and the like thrive on a darker future though not necessarily a post-apocalyptic one.