The core rule book is great, and you should get it, but this one is like the core book and then some. It has all the rules of the core book plus much more on character generation and additional, updated, hero datafiles. I've been GM'ing this for a few weeks now and the game is awesome. I've played and GM'd everything from Top Secret S.I. to Traveller TNE. Yes, I also played and GM'd the old TSR Marvel game and Marvel Heoric Roleplaying beats the crap ouf of it. Remember how, in the TSR game, more "normal" heroes like the Black Widow or Captain America couldn't match up again'st most mutant characters? Not so here. It's not about power rank vs. power rank because you use dice pools. You roll the dice from several different traits, like powers and specialties, and compare those. So it is totally possible for a hero like Captain America to take out some of the more "powerful" villians. Weapons even work much differently in this installment.
Trust me, a guy who's been gaming since the mid-eighties.. if you like Marvel, and you like role-playing games, you gotta have this!