I'm gearing up to GM this AP once our Rise of the Runelords campaign wraps up in a few weeks, and this volume has me very excited to see what the rest of the path brings. Originally I wasn't planning on running it -- while I found the concept extremely exciting, the high-level play coupled with mythic was turning me off of it (I much prefer running lower-level games).
After reading this though, I don't think I've ever been quite so excited about the direction an adventure path is taking. The opening is great, and I even love those first few encounters against vermin -- I love the contrast of that, after the characters having just witnessed the scene in the city above.
Of special note are the NPCs. The four major NPCs are fully fleshed out with interesting personalities and rich stories, and reading about how Anevia and Irabeth met and fell for each other made me tear up a little bit.
Of course, this leads to the "controversy" that's engulfed this forum about Anevia. I'll put it in spoiler tags so that those who aren't interested in this ongoing conversation can just ignore it.