A great product in my opinion as essentially what it does is sift through four previous generations of D&D products to bring to you an in depth look at the politics, culture and even biology of the Baatezu. The writer does more then just use previous sources but also utilizes his own creativity to help fill some holes in the confusion caused by the nuanced lore changes that are inevitable with the advent of each new edition. This really appeals to me as one of the biggest problems I run into with 5th ed is constant edition confusion where players understandably think that either old rules or old cannon still apply. It gives stats on not only many different kinds of devils that could not be included in the official WOTC releases but gives you all the necessary lore you’ll need to understand their place in the infernal hierarchy and how to employ them. Given as I am hardcore geek the thing that really appealed to me was that he also included stats on all the most note worthy Arch devils. It has always been my experience that most D&D fans tend to favor demons over devils, and WOTC’s choice to include the stats on demon princes in the Out of the Abyss story arc would seem to hint in that direction. After all who doesn’t awe at the psychotic, two headed psychosis of Demogorgan or tremble at the vile undead power of Orcus and his dreaded wand. However the problem with demons can be that when a party encounters them, with the exception of the Glabrezu and minions of Graz’zt, most Tanar’ri just want to eat you. Devils want souls, and to that end this book makes it clear the more pure the soul the more power they can wring from it. Thus it has been my experience that devils can offer a much more gratifying role playing experience in which you can test the moral metal of your players, or just give them a first class ticket to hell if they think that it’ll be more fun. With this book you know which devil is likely to tempt the players most, how they’ll go about doing it, and which Arch devil they most likely report to. All in all I think this is exactly the kind of product that 5th ed needs and I sincerely hope the writer does in fact do exactly as he hints at in the text and gives the Demons of the abyss the same treatment he gave the devils of the nine hells.