I'm not really into sci-fi. But Starship Troopers was surprisingly good. It's a first-person narrative of a "Mobile Infantry" soldier in some future, intergalaxy war. Although the weapons and "Navy" - read "spaceships" are different, the infantry and Navy maintain traditions dating back to "surface ships" powered by wind sails and earlier.
And the book is quite philosphical, offering a strong critique of America's current system of deterring crime, especially in youngsters. According to Mr. Dubois, the narrator's professor of History and Moral Philosphy, "juvenile delinquent" is a contradiction in terms - and treating someone as a juvenile delinquent until they're eighteen, then giving them capital punishment, is like letting a puppy make messes inside, then killing it for doing the same when it becomes a dog.
Also according to Mr. Dubois, any moral philosophy must be based in survival; otherwise, it's worthless. Almost Kantian.
And the author takes an interesting perspective on voting: only veterans are allowed to vote in the narrator's society. Why? Because they've shown they care. Anyone not willing to lay his life down for his country has no right to guide his country's decisions. This, at first glance, seems to fly in the face of the Western idea of civic militarism. According to Victor Davis Hanson, the West has won because its soldiers - from Greek Hoplites to U.S. Marines - have a say in their government. They care more than a conscript; they fight for freedom, instead of fighting from fear.
Yet the infantry in Starship Troopers still fights for freedom - they just don't have total freedom yet. So, theoretically, it still works.
Even if you're not into sci-fi, I'd recommend this book. It's a quick, and thought-provoking, read.