This product heavily features the Nashi ancestry, essentially raccoon-folk. In addition there are character options for the alchemist as well as a good amount of supplementary info on firearms (and the equipment therein).
The Nashi Ancestry options are quite varied and are packed with flavor text, particularly in the beginning where things like culture and architecture are discussed. The ancestry includes 10 heritages, a veritable boatload for players to choose from. This also includes a suite of ancestry feats that tie the aforementioned flavor text quite well with mechanical bonuses.
The Alchemist options primarily revolve around the use of firearms, especially alchemical cartridges similar to what you may remember from pathfinder 1st edition. The options within are very thematic and relate well (again) to the Nashi themed supplement.
The sorcerer and wizard also feature briefly, with a Tanuki sorcerer bloodline themed for trickery and illusions (of sorts) and a wizard school that expands on the wizard's ability to get extra arcana/crafting skill feats as well as crafting proficiencies. I'm particularly partial to the wizard school, as its a pretty big departure from the other wizard options in core 2nd edition.
There is also a single dedication archetype included, the tinkerer, which again utilizes earlier themes to good effect. Basically does exactly what it sounds like.
Finally come the firearm rules, which are more oriented toward a steampunk style campaign setting, and are pretty varied because of it. While the setting may be rather specific, I think anyone running a game where firearms are more common could definitely use these rules.
The alchemical cartridges are quite well written and may actually be my favorite part of the supplement. Including Bolas, dragon's breath, and more, this part shines and could be used for any game running firearms, even if you're using some that are more oriented toward earlier-age firearms.
All in all the book is great, the options are wide and interesting, and the art is great! (I forgot to mention this earlier!) Would definitely recommend picking this up if you have interest in using steampunk/magicpunk style firearms in your game!