MHR is a powerful, but limited tool. If you're a comic book fan and you know and love the stories, it is a great method for retelling them and spinning your own. What the Civil War Event Book is really lacking is guidance for the GM who doesn't know the stories by heart. Likewise, it is challenging to play the heroes with only the materials available. There's a brief history and roleplaying tips in the form of experience point bonuses which are great and really useful if you already know the characters and their stories. If you're coming at the game from a position of less knowledge the game really doesn't close the gap well enough.
If you're a big fan or you're willing to do the research (fun research!) I recommend this game product very highly. But it's not for everyone.
[4 of 5 Stars!]