I think the problem is that the chapters are so short. You think, "Oh, well, I'll just read one more, 'cause they're short," and the next thing you know it's waaaay later than you expected.
I liked it a lot, though. I don't really like the guy's writing style, but I thought the story was great. It kind of contradicted a lot of the stuff that I've been raised with as a Catholic, or at least cast aspersions, but it was really, really interesting stuff to consider anyway. And I love all of that conspiracy theory-secret society-ancient grudge thing. If you haven't read "Angels and Demons," you should read that, too.