I myself am a huge fan of the demon princes, a true die-hard worshiper of Demogorgon. This book promised all the demon princes and devil lords, and to be honest that would have been enough. It delivered not only excellent stats of the demons and devil rulers (even better then I'd first expected), but also tones of other vile treats, interesting prestige classes, drugs, torture, and feats. All of which balance well within the game, the ''warning! Content is intended for mature audiences only.' Sticker served only for amusement, since the only truly nasty stuff was a feat called 'Lich loved', and reference to not all that tasteful sexuality, 'bestiality', 'necrophilia', 'sadism', and 'masochism', all of which can be easily avoided as they are clearly marked. Demonic possession adds an interesting level to the game, as does the introduction of some nasty diseases, if you are planning on involving demons, devils, and other lower dimension entities then this is a good buy, if you are planning on running a campaign in the planes using manual of the planes then this is an excellent buy, if you want to run an evil party or have an evil character then this is a essential buy, and if none of the above apply to you then this is still an extremely interesting buy. Overall this book works best with epic level characters, having said that, many ideas for lower level characters can be found. I would not buy this if I was just starting out as a DM, or player, but if you've got some other supplements like epic level handbook or manual of the planes to back this book up I'd say it is well worth the money... now were did I leave my Vasharan Offal bag?