About to depart on his first vacation in years, Edward Wozny, a hotshot young investment banker, is sent to help one of his firm's most important and mysterious clients. His task is to search their library stacks for a precious medieval codex, a treasure kept sealed away for many years and for many reasons. Enlisting the help of passionate medievalist Margaret Napier, Edward is determined to solve the mystery of the codex-to understand its significance to his wealthy clients, and to decipher the seeming parallels between the legend of the codex and an obsessive role-playing computer game that has absorbed him in the dark hours of the night.

The chilling resolution brings together the medieval and the modern aspects of the plot in a twist worthy of earning comparisons to novels by William Gibson and Dan Brown, not to mention those by A. S. Byatt and Umberto Eco. Lev Grossman's Codex is a thriller of the highest order.