Typically solid work from Chaosium that takes a well-worn fantasy trope -- living in the trees -- and says "lets break that down and see what it would actually take to have a society there; why would people live in such a challenging way?" I mean there's a reason we don't live in the trees now. It's impossible. The Green shows us how it could work, given of course the existence of magic and goblins and ape dudes.
The presentation is very good. The photoshopped photographs are a bit funny looking, but the style is unified throughout so it suits itself just fine. The writing is clean and intelligent. All in all, a very good overlooked product for people who want a challenging, internally realistic take on this idea. Fully statted for BRP in the typical clear style of Chaosium.