Based on the authors experience in the Vietnam war but translated into a science fiction universe, the Forever War is a great read and a definite must for any real Sci-Fi fan.
It follows the wartime experience of a single soldier who, because of the time distortion of space travel, finds himself dislocated from the Earth-bound society he knew while dealing with the real-time machinations of successive Govenments, whos sole purpose is to win a war that no-one knows either the reason for or the probability of success.
Just fast forward the time it was set (the interstellar war begins in 1996) and go along for the ride, you won't regret it.