This is really one of the best supplements / wilderness worldbuilding books I've ever read. It's fleshed out enough for low-prep gaming, and also inspirational for DMs to build on top of. 

I stumbled across the physical copy of this book first, and I am so glad my game store stocked it. It's a high quality physical book I'm glad to have on hand. I loved it so much, I had to get the digital version as well. It's nice to see the added value in the digital downloads, making it worth buying twice.