My personal favourite sci-fi books are the Hyperion series by Dan Simmons.
Not (commercially) available but I downloaded the series recently from a torrent site for free
yes I know naughty naughty but I would`ve bought them if they`d been available anywhere.
For post apocalypse (very far past the apocalypse) try The Book of the New Sun series by Gene Wolfe, so far in the future it`s almost the dark ages again apart from strange "run of the mill" things like aliens and star ships which pop up amongst the dirt and backwards technology.