The parts of this novel that kept me reading were the instances when the main character had the opportunity to demonstrate his (the author's research) theories regarding the history of the church and their use of symbols in creating a story-line to be lapped up by the masses. The destruction of the feminine mystique as perpetrated by the church, is a running theme throughout the book, as well as how famous artists railed against the church through the slew of hidden messages and symbols in their work as a means to give voice to what they believed was the real story of christ without tipping off those for whom they were often commissioned to do work...i.e. the church. Another theory woven into the story is that it is a lie that Mary Magdalene was a whore when in fact she was (apparently) from a well-to-do family and thus was a perfect match for christ and also that she and christ had a child.
Behind the heretical (to the church) variations of history are the secret societies known as the Knights Templar, and the offshoot organization that is even more select and ethereal, the Priory of Sion, with supposed famous members through the ages including the likes of Leonardo da Vinci and Victor Hugo. The existence of the Priory of Sion is highly doubtful, but its claimed raison d'etre as laid out in The Da Vinci Code (and numerous other books, essays etc.) is keeping the Holy Grail hidden and protected and deciding upon its eventual unveiling at an historical appropriate time to do the most damage to the church.
Though I mentioned that the author, Dan Brown, seems to understand the use of plot, the twists themselves are absolutely fraught with cliches, as is the use of language. That he was obsessive about research and truly intrigued by the story idea is evidenced by the fact that the most compelling passages are when part of the theory that drives the story forward is being doled out by Langdon, when he is regaling another character with his knowledge. Handled in a less deft fashion, this book would be roundly dismissed as an awkward vehicle for a conspiracy theory. Because of the attention it has gained, many are of course doing just that, but it is also sparking countless others to casually accept the claims outlined in the Da Vinci code.