I'm going through a Heinlein phase. Recently I got in a discussion with someone about Heinlein's "Starship Troopers." I mentioned that Halderman's "Forever War" was essentially a rebuttal to "Troopers." If you've not read one or either of the books, this won't make much sense, but I do hope to review both eventually.
In essence, Starship Troopers was effectively "Heinlein's Republic" - Trust soldiers to defend democracy, trust soldiers to run democracy. Ostensibly a war story, it's remarkably unconerned about the war, and goes on for chapters at a time, ideologically explaining how society should be arranged, and explaining why it should be arranged that way. That's not a criticism. There's a definite appeal to Heinleinian Democracy, particularly if you're a center/right Libertarian.
It's very gung-ho, very can-do, very optomistic, very post-WWII John Wayne-With-Brains, very Social Engineering-y, if that's a word (And if it isn't, it is now). It's very "this works on paper, therefore it'll work in reality." Heinlein was, at root, an engineer, and he tended to view society in mechanical and logical terms. As a kid, I found this reassuring, as an adult, I found it quaintly naive. Nowadays, I find it annoying. Despite its disconcertingly preachy tone, it's a fun book, and it's hard not to like it.
Halderman's "Forever War" was a more realistic portrayal of war: things go wrong more often than they go right, no one ever has a clear picture of what they're doing, or why they're doing it, goals are obscure at best, completely nonexistent at others. Unit cohesion is a serious problem. Society changes drastically (Think how clean cut everyone was at the start of Vietnam, and what people were like when it ended) Politics change during the course of the war, and therefore change the way it's fought, again and again, and when all is done and said, the entire thing was a fools errand. It's a total FOBAR from start to finish, and a compelling one. With a plot, which, automatically, just by virtue of having a solid story, makes it a contrast to "Starship Troopers," which deliberately makes the larger storyline hard to follow, so we can focus more on the political theory aspects of the novel.
Let me be less snarky: "Trooper" is an idealized view of war and society, and "Forever" is a more naturalistic portrait. One's an engineer treating life like an engineering problem, the other is about a person trying to survive a physics problem. One is a story about a World War Two styled conflict with reasonably clear good-and-bad guys, and a fully committed industry and military and political establishment fighting it together, just like when we whupped them dadburn Nazis. It neglects to consider that World War II was the anomaly, and most wars are far less popular, and far, far messier. "Forever," by contrast, posits Vietnam in space, and focuses on the human angle.
Way too pointed summary, bordering on unkind: "Trooper" is a book by a Navy guy with no combat experience telling Marines how to fight, and also a book by a guy who lost an election but has no other political experience telling us how the government should be run. "Forever" is a book by an army grunt who actually fought, and was wounded in combat, and who has no illusions about politics.
One is dialectical and theoretical. The other captures the whole "Holy crap! This is both awsome and horrible" quality.