I read this novel very quickly and defensively, to be honest, because it includes an attack on some fundamental aspects of Christian religion. The story is well developed, although the bad guys are an obvious caricature of a real-life Catholic sect. I love the idea of using art as a tool to solve a murder, and an alternate version of Christ's life and history would create a strong motive for the bad guys. So the book is good, if it is taken as a simple mystery story.
The book fundamentally misunderstands Christ's significance and the role of the church in society, though. Biblically speaking, the church is designed to be the body of Christ. As such, it should strive to be fundamentally open to all sinners who acknowledge the need for a savior. The church is imperfect at this mission, but it is far from being the secret mafia that the Da Vinci Code makes it out to be. Furthermore, Christ was not just a man, he was the embodiment of God on Earth, completely human and completely divine. The Da Vinci Code wants to treat Christ as if he were simply human, and substitutes any divine characteristics he might have with the pagan symbology of male and female gods and goddesses. It creates a false version of Christ, which is no different than other versions that have been around for centuries, if not millennia.
The attractiveness of the other versions of Christ is that they are different, but I know that Christ was indeed both human and divine. He is the only living God, who was made flesh, crucified for the sins of the world, and rose again. The authority he has in heaven and earth is demonstrated in the true Biblical accounts of Christ. I know this is "accepted dogma," but that doesn't make it any less true.
The Da Vinci Code, for all its inventiveness, does not fundamentally offer anything new to discredit the Christian religion. It is a good read, but I would warn against reading it anyone who has never encountered the living God or who has not read the full Biblical accounts of Christ's life, death, and resurrection. The false version of Christ in the Da Vinci Code is enough to warrant a "thumbs down" recommendation from me.