I read the Da Vinci code and like it as did all my friends that I loaned it to. It didn't have a lot of good character development, which I really like in a book, but the story and plot were quite good. I found it almost *exhausting* in that the story takes place over a 48 hour hour period. That was kind of strange.
As far as the stuff that is presented--I think Dan Brown did a good amount of research I immensely enjoyed the religious history he presented. I believe most of it is factual (not that this stuff is proven) but that these theories of Jesus, Mary, etc have been around a long time and written about extensively by others. The theories presented in the book are quite believeable and I would imagine many Christians would find the book disturbing or a *joke*. I found it very enlightening and it explained many things to me, and built upon many other things I have learned. The Priory de Sion actually does exist and Leonardo Da Vinci was the head of it at one time. I found several documents during my research that show the original "Last Supper" painting does, indeed, have a woman seated beside Jesus. Also, the Last Supper was *restored* several times and had that image removed at some point. I think, since then, it has been restored back to its original state.