The latest volume of Brian Wood's DMZ, Friendly Fire, is the best one yet. The two creators have managed to take their story of an embattled New York City and turn it into what is the most challenging morality tale in recent history.
The basic premise is that an American soldier is being tried for participating in a massacre of civilians. What ensues is an incredibly in depth look into what happens when wars go wrong. In this story no one, whether they be killer, victim, or observer, is innocent yet everyone is entirely justified in their actions. This book has risen from being one of the best comics today, to being something important.