From the back cover:
"Diabolical threats lurk everywhere in the world of the AD&D game. Heroes who fight evil on the Prime Material Plane may contend with forces whose power rises from the depths of Hell. Adventurers who travel to Hell meet devildom on its own terms and risk not only their lives but their everlasting souls.
"Guide to Hell is a comprehensive look at the nature of devils, ways for heroes to battle them, and the twisted geography and politics of the Nine Layers in the AD&D game. The decision to "go to Hell" should never be made lightly – but once it is made, this book will give the DM everything he or she needs to make the experience memorable for all the heroes ... at least, those who survive."