How much of an influence was Robert Shea and Robert Anton Wilson’s Illuminatus! Trilogy on the writing of this book?
No direct influence. Despite the parallels noted by several reviewers, I’ve never read The Illuminatus! Trilogy. It’s possible I picked up some of the flavor of Shea and Wilson’s work from a secondhand source—like Steve Jackson’s Illuminati card game—but I think most if not all of the similarities are just coincidence.