Anyways, I'm not going to post a comprehensive review, a) because I'm not that far in, and b) because it would be easier to provide a link for an existing review (the one that inspired me to buy the book, in fact). No need to reinvent the wheel. Essentially what this posts amounts to is another recommendation of the book. It's well-organized, and the ratio of inspirational fluff to the nature/origins of the Underdark to actual locations and monsters seems to be pretty spot-on. I'm sure that many people might prefer more "crunch," but I have enough monster stat blocks on the DnDi Monster Builder! So while new monsters are always nice to have, I appreciate that the section was relatively short. Also appreciated is a list of monsters from other products, organized by which areas of the Underdark they are most likely to be encountered. Sweet! It's helpful, going straight to the point without taking up much space.
The prose is fairly engaging, especially considering that the style of most D&D books tends to cause my mind to wander. At first I figured that the origin story and history of Torog would be a section that I'd struggle to maintain interest in as I tried to breeze through it as fast as possible, but it was actually one of the more interesting reads in any D&D book. Torog may be one ugly mofo (he's pictured toward the back of the book - not for the faint of heart), but his characterization is just downright intriguing. A lot of it comes from the complex relationship that he has with other beings, given that he's an evil god. During the Dawn War, all of the gods (good and evil) were fighting together against the Primordials. Torog got royally screwed over by his Primordial nemesis, who cursed him just before Torog finished him off. Essentially, Torog's wounds never heal and he can't leave the underdark. His throes of pain carved out some of the widest passages, which are now known as the King's Road and still contain splatters of the god's blood. Essentially, the rest of the gods abandoned him down there, though because of the curse he can't get back to the Astral Sea anyways (his power quickly diminishes upon leaving the Underdark). The perks of this arrangement are that he is the only god that has a direct influence on the world; the rest are forbidden to meddle in the affairs of mortals by the Primal Spirits who expelled both the gods and the primordials from the world toward the end of the Dawn War, so that the very world that they were fighting over wasn't destroyed in the conflict. Of course in the deepest parts of the Deeps there are rifts to the Far Realm, and so Torog is also a kind of guardian of the world, keeping abominations from the Far Realm at bay. Talk about a case study in contradictions! His relationship with Lolth and the Drow, who also share dominion of the Underdark with him, is complex but somewhat wrapped in mystery (followers of each god have their own "version" of things). And to top it all off, he has somewhat of a death wish, and who wouldn't given an immortal life of endless torment?
If only more of the gods were given such vibrant personalities then perhaps I would show more interest in the D&D pantheon.