Let me just start by saying that there really isn't anything wrong with this book. It is just as good as The DaVinci Code or Angels and Demons, which were both enjoyable books. As a matter of fact it is not only just as well written as those two books, it follows the same basic formula. I find it unfortunate that writers of series find it necessary (or just too easy) to stick to the same formula that worked for their first book over and over again.
If this is the first book by Dan Brown you've ever read then I think that you may enjoy it. Or, if you thought that Rambo III or the Police Academy movies were good, then you may be able to overlook that blatant use of a cookie-cutter formula and really enjoy this book.
I, however, feel that reading a book is a significant time investment, and I want to get a little better return on my investment than this. Because I've read the other books in the series, I knew from the beginning that our hero was going to solve the puzzle, but just in the knick of time. I knew that some secret society that had been working on the fringes of society for centuries was going to be under attack by a madman bent on exposing their secrets. I knew that the timeline was going to be short and tense. I knew that several characters were going to be killed off throughout the book. I knew that the bad guy was going to have another motive than the one that seemed so apparent. I saw the 'twist' coming twenty pages out, and I wasn't shocked at all. And, the ending was a bit of a let down (formula or not).
All in all I think I have to give this book only 2 STARS. Sorry Dan Brown, you just don't do it for me.