Neuromancer by William Gibson.
The Forever War by Joe Haldeman.
Rendezvous with Rama by Arthur C Clarke.
A Fire Upon the Deep and A Deepness in the Sky, both by Vernor Vinge.
Also, the Culture series by Iain M. Banks, but I would recommend not starting with the first published book, Consider Phlebas. YMMV, but I personally found it hard to get in to and almost didn't continue the series. Later I read lots of reviews of the second book, The Player of Games, and decided to give it a chance and have since read most of the remaining books. I have now gone back and re-read Consider Phlebas and love it now that I have a better handle on the setting, universe, and concepts from the series, but I definitely feel that The Player of Games is a much better intro into the series.
Also, the Culture series by Iain M. Banks, but I would recommend not starting with the first published book, Consider Phlebas. YMMV, but I personally found it hard to get in to and almost didn't continue the series. Later I read lots of reviews of the second book, The Player of Games, and decided to give it a chance and have since read most of the remaining books. I have now gone back and re-read Consider Phlebas and love it now that I have a better handle on the setting, universe, and concepts from the series, but I definitely feel that The Player of Games is a much better intro into the series.