The Short-Timers by Gustav Hasford
Good luck getting a copy of this book - but if you manage to, you won't be able to put it down. Kubrick's Full Metal Jacket is based heavily on Hasford's work, which follows American marines from their training base to Vietnam. Capturing a pathos only present in as senseless and surreal an environment as war - you'll wish The Short-Timers were longer.
Buy it HERE, but be warned, the prices are insane.