The Forever War by Joe Haldeman
What struck me most about this book was how it didn’t seem aged at all, despite being written thirty years ago. The setting is super-futuristic, but it is the commentary on war that is truly timeless.
The Earth’s leaders have drawn a line in the interstellar sand – despite the fact that the fierce alien enemy they would oppose is inscrutable, unconquerable, and very far away. A reluctant conscript drafted into an elite military unit, Private William Mandella, has been propelled through space and time to fight in the distant thousand-year conflict; to perform his duties and do whatever it takes to survive the ordeal and return home. But “home” may be even more terrifying than battle because, thanks to the time dilation caused by space travel, Mandella is aging months while the Earth he left behind is aging centuries …