This is not so much a re-writing of Manga! Manga! as it is an addendum. You won't find anything in repeated here that is already in Manga! Manga!. You can read it by itself if you want, but I think you'd need to read both books to really get the full experience and become fully informed.
There's even an entire section talking about the debate over Disney's Lion King ripping off Tezuka's Jungle Emperor Leo. How great is that?