This is an in-game book for the Mythical Journeys LARP, although it could also be used as a resource in a tabletop roleplaying game. Radiance is a religion concerned with doing good and thwarting evil in the world. See http://www.mythicaljourneys.com for more information. With the dust jacket removed, it can be used as an in-game prop.
This book collects several works: The Books of Radiance; Dedication Ritual to Radiance; Eliwen Asiran's "On Radiance", an overview of the religion; Romariath Thale Aldtho's "Avatars of Radiance", which provides more information on the Avatars. Together, these provide the cosmology, theology, history, and dogma of the Radiant faith.
There are a total of 61 pages of text, plus table of contents and index, and additional blank pages at the end for notes.