Batman also has epic moments in the "New World Order" arc. I'd explain things in the arc...not a lot, but J'onn would give brief explanations of the Civil War and it's factions and what eventually happened to Mars its self, not to overwhelm the audience or take them out of the movie, but enough to make them understand what's going on.
Anyway...my pulls for tomorrow are the following:
-Action Comics #17 (Morrison reveals the death of the Kents in this issue)
-Justice League #17 (Conclusion of the Throne of Atlantis arc)
-Wonder Woman #17