Gods and Monsters fills a number of gaps left in the line up for M20 like Companions, Familiars, spirit-forms, god-heads, and a fair number of Bygones. There are still considerable holes not yet filled but Technocracy Reloaded and Book of the Fallen but a book they have to come out in some

Good parts:

• Every creature is illustrated
• The rules for roll-your-own entities are remarkably thorough and cover "sentient cell phone" through "embodiment of an island in the form of a dragon". Which says something.
• The crossover rules are exceptional and do a remarkably good job of allowing a storyteller to introduce other lines very quickly without buying a 600 page X20 book.
• Entities are introduced along either a theme or in a family. The section on Yaruba through Afro-Caribbean through Louisianna voodoo is reasonably fleshed out and doesn't have just one example for a given idea.
• Stats for "normies" are given such as for kids and the old. Sometimes it's useful to know how many health levels a teenager has and such.
• Areas undercovered by other urban fantasy games are well covered. Characters break most forms of normativity in relationship types, identities, and such.
• Some of the points of view are very angry and the points of that rage are easy for for an ST to incorporate.
• Soe vague prior systems are really tightened up or explained. God-forms were often presented as being whatever a viewer's culture expected, but this can get super messy when items don't quite line up.

Bad parts:

• The art just doesn't pop like other books. None of the illustrations besides the cover and some of the chapter openers are on par with the quality and imagination in other books. They feel like rough drafts. This may be due to budget and I get that but the bar is high and I don't think that bar is met.
• The points of view are confusing. Mage usually has say three voices. The "systems" voice which explains systems and maybe behind the scenes stuff, the "book author" voice which explains the setting in a somewhat clinical or impersonal way, and "character" voices which bring the emotion to the party. And those parts blur like when describing djinn. In Lost Traditions, djinni are described as cruel and lazy where in this book humans are blamed for everything. Likewise, the hatred of outsiders for some of the Pac Rim entities is either racism or xenophobia in a modern gaming context. If the justification is "colonialism", sure, but I feel that opens the door to a lot of things, again, which is fine, but it felt messy in many points.
• Some of the descriptions simply went on too long. One avatar type got an entire page where others were a 1/3rd of a page and just if not moreso interesting.
• No advice is given to the storyteller as to how to run stories with cultures outside their own. There's some explanation in the core rule book but I really think it'd make sense to re-iterate it here.
• There are errors and some holes. Some things are simply not explained like the Size, Rage, and Gnosis traits. There are some typographic errors. It's a lot of stuff and almost impossible to get right. It's sad that revisions would be so hard so thanks White Wolf.

Overall: Get it. It's $15 and it's 225 pages of rules, entities, and art. That's less than ten cents a page and that's at full price. If somehow that's not good enough, wait for it to go on sale. It's way better than what you could get for $15 on the ST Vault or a used book store.