This book should be considered required -- not because of how amazing it is, although it is, but because it seems most other supplements assume that you have it and they will reference powers in it with no explanation whatsoever. It's annoying, really. The Powers section in Icons: Assembled should just be replaced with this book, because the core book is more-or-less incomplete.

That said, this book has tons more powers that aren't in the core book and offers more detail for many that are contained within the core book. It really is essential.

An unusual reference which mixes essential information useful during play with stuff that is useless. I printed some of these pages as references to have on the table for all players, but some pages are a mix of things useful to players and things only useful to the GM. It could use a reorganization and a replacement of some information, such as removal of the character creation stuff to make more room for stuff you need to look up on the fly during a session. I ended up crafting my own cheatsheet to print out for players to understand how to use qualities/advantage/trouble.