James Jones' From Here To Eternity...there's a lot to this book, and if you only know it through the (rather good) 1953 movie then you don't really know it at all. It's been called the best novel about the pre-World War II Army out there, and insofar as it gives an unsparing portrait of the Hawaiian Division before the war that may be true, but that really dates it far too much. Where the book really shines is in its equally unsparing look at the kind of men who enlist in a peacetime army and the kind of men who run that army, and that's not always a very pretty picture. My father got the copy I now have as part of a set with The Caine Mutiny and The Naked and the Dead, neither of which are anywhere near as good as this. Well, Wouk's book, maybe; certainly on average Wouk was a much better writer than Jones, as a quick look through The Thin Red Line and Whistle will tell you. I probably read this for the first time when I was far too young to understand it properly or fit it into the right context, but there you are. Holds up very well to multiple re-readings.
I made an exception for Hans Hellmut Kirst's '08/15 im Kaserne (The Revolt of Gunner Asch) and its sequels, which I read in their Pyramid translations back in sixth grade. These were pretty remarkable books, depicting as they did the WW2 German Army in a very unsentimental light as an organization capable of driving its own junior NCOs to rebellion in the name of justice. Kirst had a gift for producing memorable, sympathetic characters, and even though I haven't cracked these in years I can still see Asch, Vierbein, Lieutenant Wedelmann, and Colonel Luschke as if I'd just put the books down yesterday. Kirst also wrote a whole mess of other books about the Wehrmacht, of which Night of the Generals is perhaps best known thanks to the movie, but these are arguably the best.
I have to admit, I like the movie version of David Westheimer's Von Ryan's Expressa lot better, even though the book does a better job of explaining why Ryan is such a martinet and also has a sequel, which the movie can't. Still, the book is excellent, quite the period piece and an interesting counterpoint to Hogan's Heroes. Sorry, no deep meanings here, just a book that spawned an excellent movie...and made it possible for me to find Westheimer's Lighter Than A Feather, one of the two novels spawned by the stillborn Operation OLYMPIC/CORONET.