Originally Posted by chaymus
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.
I absolutely adore Dune, but the universe Dune is set in is full of hope. I wouldn't even consider the God Emperor portion of Dune apocalyptic, more forced evolution through a benevolent dictatorship.
Games Workshops 41st Millennium is a brilliant example of far futuristic, morbid, bleak sci-fi. The miniatures game/video games are a terrible indication.
Check out the writings of Dan Abnett though, Dan is one of my all time favorite authors, I have challenged Lit majors to tackle it, even with their obvious bias due to the nature of the source material and they have been spellbound by it.
Eisenhorn is an incredibly beautiful yet action packed trilogy, a moving and starkly human portrait.