This is a very interesting book. Reading this, I definitely understand why everyone was saying that this is an experiment. It's much lighter on rules content than I had expected, which I admit took me out of it a bit until I figured out what they were going for. It presents a look at various NPCs, but what it really does is provide a ton of adventure hooks that can take a party throughout the Inner Sea and beyond. These hooks are informed by how these people relate to each other and what that means for the Inner Sea as a whole. There is also information about them as people, which will be very useful to a GM who has to play them.
One of the strengths of the plot hook format is in how it contextualizes the various NPCs. An NPC who is an invaluable ally in one plot thread might be a bitter enemy in another. There is a good mix of new characters and old favourites, with new information being given to certain figures. Have you ever wondered how Old Mage Jatembe became immortal? Or why the inevitables haven't gone after Artokus Kirran? Here, there be answers. There are references to characters even beyond those spotlighted. Some of them are old friends, including a Pathfinder Tales protagonist (and no, not Varian or Radovan).
I highly recommend this book to anyone who wants to know more about the Inner Sea and is not afraid of spoilers. Not every First Edition Adventure Path is spoiled, but more are than are not. I for one am glad to find out some of the canon endings for the newer APs. One aspect of one of the endings put a huge smile on my face. I had hoped that character would get that ending after all of the abuse he suffered.
All in all, this is a successful experiment. It's certainly one I hope to see repeated. There are a number of figures who are prime candidates for this treatment, and I'm sure there are plenty of new characters waiting to be revealed.
