The Forever War, Almost anything from Peter F Hamilton (perhaps the only book of his I was unimpressed by was Market forces, making executives fight each other to death for jobs... nice idea just a bit dull compared to his other works). If you don't mind going a bit lowbrow / young adult there is a very good star wars trilogy by Timothy Zahn that takes up after the end of return of the Jedi, its quite old now and Lucas lifted a number of his ideas for the prequels (and then utterly ruined them btw). Anyhow, its the Thrawn trilogy, starting with Heir to the Empire. 'Do androids dream of electronic sheep?' is another good one. Neuromancer is classic which was required reading for me at university. Oh Richard Morgan's altered carbon is also really good.