An exceptionally well written and fascinating book. We follow William Mandella through his military career in a war that spans centuries of time and many light years of space. Due to the time dilations associated with near light speed travel, it is perfectly possible for one individual to be around for just as long, assuming he can survive the exceedingly high casualty rate of their battles.
One of the most interesting things about this book is learning about the social and cultural changes that have transpired to earth's people while William has been travelling across the galaxy. Taking only months of his subjective time, many years have passed for those back on Earth and William increasingly finds that he has become isolated from the rest of humanity, an anachronism from the past.
War is harsh and inflicts a heavy toll even on those lucky enough to survive it. The madness and futility of war, exasibated in this case by being drawn out over so much time and being fought for reasons that no one really understands, is really brought home to the reader through William's experiences. An insane arms race leading to unpredictable battles in which you have no idea whether you are going to face a foe more or less technologically advanced (depending on who's spent more subjective time travelling at close to light speeds).
The best thing about the book though is that it has dated exceedingly well. It doesn't feel like it was written over thirty years ago and it's allegorical message is as relevent today as it was in the 70's.
Haldeman's writing style is slightly cynical but highly engaging and a pleasure to read. I can't wait now to read something else by him.