From the back of the book:
The Abiding Book is the most sacred of all God Learner scriptures. Written by the hand of the Invisible God himself it documents the mythical history of the Malkioni, prescribes the nature of worship, truth and heresy, and forms the basis for all sorcery grimoires in use and at large across the Middle Sea Empire. It defines the God Learners; guides them, informs them and sometimes, misleads them. It may be the most powerful accumulation of mythical knowledge anywhere in Glorantha: it may also be the most dangerous.
The Abiding Book for Second Age Glorantha is a highly detailed overview of the Middle Sea Empire: its people, its territories and dominions, its hopes, schemes and ambitions, its myths and its magic. Within these pages you will find a wealth of information concerning every aspect of God Learnerism. From descriptions of its great cities through to profiles of its psychology. The nature of sorcery and the empire's approach to it is examined and the book offers more spells, new grimoires and new sorcery orders to fuel God Learner campaigns. With this book you have everything you need to explore the Middle Sea Empire and create compelling God Learner characters.