Jarhead is some idiot's (who is now a college professor, go figure) wet dream of what he thought the Marine Corps would be like. When he found out it wasn't, he didn't let that stop him in his book. The book is all about Anthony Swofford, the big hero. A drill instructor smashed his face his face through a blackboard (wow!), he threw a guy over a bar (I've seen that too, in movies), and has a problem with authority (awww).
So it's gonna be a comedy, I take it?