I was extremely excited for this publication, so it's rather depressing how disappointing the books contents turned out to be.
The shifter class was an interesting idea, but when put down on paper is just druidic wild shape with hunter focus, in the form of aspects. It, unfortunately, never surpasses the druid in the wild shape department, and is, in fact, rather limited, and the temporary nature of all the aspects means that the shifter isn't terribly impressive in that regard either. The archetypes, both for the shifter and other classes, are interesting, but several suffer from massive drawbacks, for little to no gain. Like taking on druidic weapon/armor proficiencies and restrictions, including losing abilities for wearing metal, but don't gain any significant power to mkae up for it.
The new rules expansions are, for the most part, only thrown off by some conflicting skill applications (survival to harvest poison, but heal to take internal organ trophies?) but these are easy to ignore, or fix by homebrew. So these chapters are the most stable and useful of the lot.
One of the most exciting discoveries was the Cultivate Magic Plants feat, allowing you to grow plants that copy spell effects, but the price tag attached to them, especially when attached to something with the considerable disadvantages of being an immobile magical item, makes it entirely useless next to the crafting cost of regular magical items, especially if you have a GM that's willing to allow players to use the rules on creating new magical items. Just for an example, a goodberry bush can fully feed 2 people per day forever... for 4000 GP to craft. While you could make an item to infinitely cast goodberry for 2000 gp if you have to wear it, or better yet create food and water (for about 30000).
In conclusion, the book has a lot of cool stuff in it, but only for GMs. Players won't be able to make good use of many of the archetypes and feats as they revolve too much around staying in a single environment or working with nonsensical restrictions. While many of the feats are just too focused (or expensive) to be useful except to an NPC. GMs, grab it, it's got good stuff, but players will (and should) probably stick to what they've already got.