Honestly I'm not even going to bother to really review this book. Every nice thing about it that can be said has, at some point in the last 35 years, been said. If you happen to see a copy, you will be assaulted by quotes from authors you respect singing it's praises on every visible surface. I think it had a blurb on the spine. You will wade through 8 or so pages of review blurbs they couldn't fit on the cover, carefully chosen to represent only the creme de la creme of the sci-fi world.
They are all basically right: Haldeman took his experiences with war in Vietnam and crafted an amazing story about humanity and war and relativity. There is only one real character in it, and the ending is little trite, but those are extremely minor quibbles. The technology is very "future viewed from the 70s", but that's not a complaint at all... it's just an interesting perspective.
So yeah, I'm not going to spend any more time with this one: it's a solid, thoughtful, quick-reading exploration of war and human psychology set in a sci-fi warzone. Good times.