Gerbert, a French monk educated in the sciences and literature of Muslim Spain, has risen to the Chair of St. Peter as Sylvester II, and for a brief while co-rules the Holy Roman Empire. His friend Zosimus has compiled his writings into a book at the behest of Pope Benedict VIII. An archbishop, Arnulf, jealous of Gerbert's prominence, hears of the book and wants it to expose him as an agent of Satan.

Benedict has political reasons for preserving the book, but Zosimus must travel a dangerous road from Reims to Rome in order to present the manuscript to him.

Gerbert's Book is a suspenseful imagining of Gerbert's brilliant but fated life during the tumultuous European era just prior to the year 1000.