Gods and Monsters: originally a stretch goal for the M20 kickstarter, this book is a giant collection of nearly every kind of non-mage NPC you could want for a Mage game.
As is usual for Mage: the Ascension supplements, there are tantalizing hints of forking metaplot paths (The Enlightened Shock Corps has been canceled!), new material expanding concepts that haven't been explored since 1991 (Avatar types, new paradox spirits), new story expansions and concepts to disagree thoroughly with, and some lovely art here and there.
I'm specifically pleased to see a mention (though not a full writeup) of the alien Zigg as well as a character creation engine for companion/bygone/familiar characters.
There were a few things that I wish weren't in the book however. The more horrific monsters can be pretty grotesque, and I wish this book didn't have long passages discussing mages who were slavers. Besides mundane slavery, the book also depicts Djinns as a people broken by colonial exploitation by a Persian faction of mages. I thought this was a pretty weird choice that wasn't necessary. Djinn-binding humans could have been portrayed as having found a way to fight back against envious blaspheming spirits oppressing humanity instead of portraying Islam's prophet as the instigator of a exploitative war against a fully sapient people.
In summary, although this book has the kind of flaws and controversies that any and all Mage: the Ascension books would have, this is the kind of book every world of darkness line should have specifically so Storytellers don't have to write-up every NPC themselves. Any book that cuts down on the extensive prep time that White Wolf/Onyx Path games tend to need is worth its weight in tass.