From the introduction:
"Delve into the fiery pits of Hell and confront an array of demons and devils in this infernal tome. Tread the sunless depths, crossing charnel pits and desert planes to face the malevolent power of the various Houses of Hell and even trade blows with the Four Great Princes themselves. Sink to the lower depths, encountering The Playground of Evil Children and The Angel Prisons, but beware, delving too deeply will only lead to the Belly of the Beast.
The Book of the Hell describes the expansive waste that is the Infernum, its lands, creatures and rulers. It is a bestiary, spellbook, resource guide, gazetteer and Who’s Who for Players and Games Masters alike. The civilisation, social conduct and objectives of these fascinating beings have been fully investigated. They are far more than mere scaled and horned warriors of darkness."