It is not surprising to me that so many find the Da Vinci Code so fascinating.  People like to think that they have special knowledge, especially when that knowledge gives them license.  It is also an important thing to remember about history--it is far more important than most people give it credit.  When I was studying history in college, I was asked many times why I'd pursue that instead of something more "worthwhile," more "pragmatic."  "After all, what's so important about history--it's just something that happened a long time ago.  Who cares anyways?"

I should think that the Da Vinci Code is a perfect example of why we should care.  If you rewrite history according to your own agenda, it gives your agenda validation.  The most poignant example of this is the Nazi propaganda in WWII that convinced everyday people that Hitler and his henchmen's final solution was a good idea, based in a grand history of the Aryan race. 

The Da Vinci Code is similar in that it starts out with the presupposition that the Catholic Church is an untrustworthy, self-serving, and oppresive institution, and then the Code rewrites history to support that in order to discredit the Church, who just happens to be one of the few remaining influential forces for truth and morality in our society today.  It is a common theme, actually, as seen in most of the contemporary portrayals of the Church. 

The agenda is, of course, to lessen the influence the Church has on our society today by giving it a bad reputation.  I commented on this previously in Perpetual Absurdity.  People don't want to believe the Church because the Church tells them they can't just do anything that they want--anything that feels good.  So in order to justify and rationalize their desires to do whatever they please (and, notably, instead of confronting the issues head on through honest dialogue), they simply try to discredit the opposition by highlighting and focusing on individual personal failures or, in the case of the Code, rewriting history.  This is, of course, a logical fallacy, but it is quite effective rhetoric because most people are not disciplined or trained enough to detect it. 

In any case, I ran across a handy site today that I just had to share (and partially to make sure I don't lose track of it):

http://www.life4seekers.co.uk/TheDaVinciCode-resources.htm

For anyone who's read Da Vinci Code, I urge you to at least consider giving some of these responses a fraction of the time you gave to the Code.  If you care about truth and reality, you really should.  If you just thought the Code was a fun read and don't really buy into it, I congratulate you because that's about all the book is good for.  Oh, and it sure made the author and publishers a lot of money, so I guess that's another thing it was good for. :)