I have to say I really enjoyed it, but I'm wondering whether I should have waited to read this book before I read Da Vinci Code, because the plots just seemed too similar. Really, really similar. Similar assassins, mysterious leaders, love interests (plus the vaguely contrived romantic subplots), dead bodies with symbolic markings, etc. I might have enjoyed this more if I'd read it before Da Vinci.
I heard they're going to turn Da Vinci into a film (with Ron Howard directing), but I think this one would probably make the better film. It was more of a thriller than its sequel and I was on the edge of my seat for the best part of it. However, the violence in this one is a lot more unpleasant. *shrug* Guess it comes down to individual taste.
But yeah...I enjoyed it, all in all.