The book consists primarily of a novelized walkthrough for each game, in the form of journal entries purportedly written by the Avatar himself during his adventures in Britannia. These journals are presented in the context of two Britannian historians who, during the time of the Guardian's rise to power (just prior to the opening of Ultima VII), are researching the stories of the Avatar and debating their authenticity. Maps, item and enemy lists, and simplified, "quick and dirty" walkthroughs are also provided.
Ultima: The Avatar Adventures contains a considerable number of character details not present in the original games. For example, in these accounts the Avatar is depicted as having a romantic interest towards Jaana, where the possibility of romance with a companion is never suggested in any Ultima prior to Ultima IX. The book also suggests that the Avatar feels physical pain or an encroaching darkness in his soul whenever he acts contrary to the Virtues, which can only be relieved by performing Virtuous acts such as giving money to beggars or completing Shrine Quests.
A bonus chapter includes an introductory-style walkthrough for the beginning of Ultima VII and Ultima Underworld. There is also a lengthy interview included with Richard Garriott, in which he discusses the history and development of the Ultima series over the years, and talks about his influences when designing Britannia, its people, and its lore.
This book is highly sought after among Ultima fans; used copies, depending on condition, can command high prices on eBay and other auction sites.
The Avatar's story would be continued in "More Avatar Adventures".