I have been eagerly awaiting the Adventurer's Guide to Cthonia since I picked up the stand-alone Noble Multiclass last fall, and does it ever deliver! Both of the new Multiclass-Only classes are wonderful additions. The Noble is all about enforcing your authority over your enemy, while the Possessed's Daily Metamorphosis powers are unsettling and way cool. And that's before the Paragon Paths, Epic Destinies, Professions (which work like regional backgrounds) of every conceivable kind, and Feats. Oh, the feats. My favorite of the new feats are the Fatigue feats, which let you expend some of your energy to perform spectacular, well, feats. The Equipment chapter is hit or miss for me, but there's enough other things in here that it simply doesn't matter. Oh, and the simple system for how long it takes to find a buyer for magic items is a great addition.
One of my biggest complaints with the Adventurer's Guide is with Chapter Eight, the Commands. There are simply not enough of them, I must have more! They're one of the best innovations in the book, in my opinion, and while there are enough for proof of concept, there's just not enough of them to illustrate the potential depth of the mechanics. Similarly, Chapter Four, Feudal Obligations, provides an appealing first bite but then leaves me hanging, hungry for a fuller exploration of the idea that's just not provided in this product. Here's hoping that Alea Publishing Group gets the chance to revisit these great ideas in future products.