Joe Haldeman, The Forever War (Millennium SF Masterworks S)

Imagine a world where interstellar travel is undetaken by means of hyper-space jumps through white holes. In such a situation we follow space squaddies fighting the Forever War (so called as no-one can actually remember why or how it started). The narative follows both the battles fought and the issues of relativistic time dialation. i.e. fight one battle and when you get back everyone you ever new or loved is dead as 100+ earth years have passed. Incredibly inventive and well thought out. Halderman does have a nasty habit however of finishing his stories rather abruptly and leaving you feeling a little unfulfilled. If you've never read Halderman before this is well worth a go.....