Sometimes game sequels are not as good as the original. However, with 'Army of Two: The 40th Day' that is not the case. This sequel is even better than the first game! EA did an awesome job of continuing Rios and Salem's story while presenting you with a new one. I will say though that I wish there were more weapons as well as more weapon upgrades (some of the weapons only have a couple upgrade items for certain parts of the weapon).
However, if you want a co-op game that is challenging, fun, and overall great, this is the game for you. Even as a solo game this is a lot of fun!