Brown employs a technique not uncommon in thrillers and mysteries, and that is leading the reader down a false path so as to set up various plot twists and unexpected eventualities. The problem here is that when the resolution plays out, the cryptic build-ups in earlier chapters in no way jibes with the benign reality that the reader is then asked to accept. Sinister organizations and insidious heartless characters are suddenly harmless as if it were all imagined. If the touches had been subtler, it would have been more acceptable with the framework established. As it is, it comes off as somewhat lacking in imagination.
With regards to the plot, it appears Brown makes a concerted effort to be formulaic. In fact, comparisons to an earlier novel with the same character show enough similarities to demonstrate that Brown makes no bones about his lack of innovation and instead seems intent on polishing his own tried formula. A quick check on the fog index and other readability factors indicates that the prose style is certainly intended to appeal to as wide an audience as possible (a few samples show a fog index from 6.5-10, with most in the 7-8 range--exactly what is considered a level most palatable to the masses.)
While plot-driven, there is still an expectation of at least some character development but here they remain flat and undeveloped. In fact, I can't recall any tendencies or personality traits specific to the characters nor did I have a visual image of them in my mind's eye as I was reading--something that I normally find with most books.
The Da Vinci Code is simple to read, with a story idea that almost anyone from a western country will find intriguing. Whether you are a raging atheist or a gullible bible-beater, the society you have grown up in is part of Christendom. The influences of christianity on your own life and world view are almost impossible to deny. If you reject all that the church stands for, that denial and the opposite beliefs you hold are proof of the overarching effects of the dominant religion of any society. The allure of a hidden, secret trove of documents that could somehow bring down such a powerful organization or contain some never before fathomed truth that could alter the political and religious power structure of the world is also a concept that contains mystery.