The Forever War – Joe Haldeman
Allegorical tale about Vietnam, and an interesting counterpoint to Starship Troopers by Heinlein. A war that because of jumps through temporal portals, lasts for hundreds, thousands of years. Presents an interesting conundrum in that the main character is fighting for a people and a culture that have changed so drastically that none of the motivations seem to make much sense any more. Kind of spoiled for me by the knowledge that now a country has a hard time mustering up public support and resources for a low intensity conflict that lasts a decade, let alone an interstellar conflict that lasts for millenia.