Incidentally, the DaVinci Code was written in 2003, and not much has been said about it up until it was becoming a movie, recently. I believe many "Christian" authors have seen a gold mine in the fact and decided to jump in and take advantage. How many of these rebuttal books can you get for free, out of the author's genuine desire to inform fellow Christians? Have you seen the price tag on any and all of them? Some are even more expensive than the Code, LOL.
Most ministries offer rebuttal books for an offering, making it simply a business transaction.