The Forever War (The Forever War, #1)
A classic of science fiction with a "hard" premise: how can one fight a long-distance war in the presence of relativity? Haldeman's conclusion is insightful: in travelling to battle your technology becomes old compared to those you'll fight when you arrive, which given the speed of technological advance places the attacker at a huge disadvantage. He gives his physics human scale and a prosaic, if perfectly believable resolution.
5/5. Finished 17 November 2018.
(Originally published on Goodreads.)