It works with two players, but it plays differently. You will play less aggressive, because you have a lot of space to expand Before getting in each other's way. That said it's perfect for me. I can play some 2 player games with my wife, who doesn't enjoy direct combat as much. She's more about the empire buildup. When we have more players at the table, the more crowded board will make the game more balanced between each of its aspects.
I played 2 2player games, 1 3player game and 2 4player games so far.