I just finished this book. Hmmm, I can't say for sure how I found it. It started out fine, then became dragging in the middle, had a rather nice climax (orgasmic in fact), then became rather dull in the end. All in all I'd say that it wasn't as thrilling as Da Vinci, or as emotive as Angels and Demons, but I still laud the authors for their creativeness and interesting ideas. Plus, I think the two authors, "best friends since 8", are gay lovers.
I've just gotten a copy of the book "The Rule of Four", by Ian Caldwell and Dustin Thomason. If you're a Dan Brown, Da Vinci Code fanatic, then most experts suggest that this book is a great companion to Brown.
This book, like most of the current thrillers in the market, is also based on fact. It discusses in detail the Hypnerotomachia Poliphili, a 500 year old text that has baffled scholar since its writing. The text has been fairly recently deciphered, about 1999. Here's a great site to learn more about the Hyperotomachia Poliphili.