I was especially eager to see this book coming. While unlike many people, I actually liked Beast the Primordial, I do agree it's not without its flaws, in particular regarding the antagonist section: while awesome as a crossover book, this game has very little to stand of its own, Heroes being the only type of villains, and being kinda underdevelopped. So I really was hoping for a new book to flesh them out, speak of the briefly mentioned "good" Heroes, and maybe even adding a new type of antagonist. Conquering Heroes did all of these things.
This book really does a great job at developping the Heroes, giving them a bit more depth and nuance: we even get a few sample ones with a decent Integrity score, showing not all of them are narcisstic egomaniacs (though we still get some of those). We get a variety of characters, and all of them have distinctive personnalities, methods and motivations, which really make some of them memorable. We even get some connecting to Hunters and Mages, creating ties to the other gamelines.
Not only that, but the book actually provides a new type of antagonists in the form of the Insatiable, which basically serve as an eviller counterpart to the Beasts. Now, some might feel like they are flat antagonists, but I think they offer a nice alternative to Heroes, and make for a good foil to prove Beasts aren't the worse evil in the setting.
Overall, a good addition to the main book. I highly recommand it.