Overview
Like the two Lost Omens books before it I consider this to be a perfect sized expansion digest book for those who wish to get more out of the setting or direct their players to further information but don't want to overwhelm themselves or their players.
It won't provide the same sorts of deep dives that the Inner Sea series of 3 hardcovers do but it is a near essential book for those looking to run Golarion set games for the first time and who wish to really ramp up their players connection to the world.
Issues
Two main issues that keep this book from being a 5* for me
1. Index: it has one section called "gods of the inner sea" that covers all of the god entries and doesn't give a way to quickly search for gods by name. Made worse that the section isn't even alphabetical, it is two alphabetical lists. A minor pain but one that comes up when I have tried to search for something mid session.
2. Core Gods: Any god from the core rule book lacks the mechanical elements from the core rulebook, meaning that anyone trying to decide who they want to take has to look between both books. This includes integral information like edicts and anathema sadly.
Mechanics
The book contains a smattering of background(singular), extra feats, items, spells along side some new domains and a lot of god options.
All nice to have but not the real draw for this book and certainly not the primary focus.
Conclusion
I have always found Gods to be one of the hardest elements of world building to handle personally, even in my own homebrew settings I tend to steal heavily from products like this.
As I said in the overview, I consider each of the first three lost omens books (world guide, character guide and gods and magic) to be essential digests of a perfect length for GMs or players who are getting into Golarion lore and want to add that bit of extra spice to the pot.