Hard to pick just a few. I think I am going with authors to sort of cheat a bit. ;p
I love me some Arthur C Clarke and Asimov and other oldskool stuff but every age had their greats. Greg Bear left a pretty deep Impression with his Blood Music, written in the 80s, and these days I really love me some Alastair Reynolds. Blindsight by Peter Watts, from the early 2000s, is another standout for me but feels kind of unfair to single out specific books cuz there are so many great ones. Almost anything, old and new, released under the SF Masterworks label is great!