That's not all that surprising, actually. As near as I can tell, that's the author's intent and he did a pretty good job of accomplishing it.
My daughter, who has been a much more dedicated Christian than I, had read the book before I did and for her, the book was just the source of frustration. She is an avid reader so she found Dan Brown's simplistic writing style to be inadequate, but at the same time she expressed to me her frustration in not being able to determine truth from fiction while she was reading.
That was exactly the sensation I got when I read the book. Many of the descriptions in the book are presented as historical facts and geographic realities, or rather as answers to puzzles we the readers never even knew existed. Dan Brown's book triggered a worldwide curiosity into the secret symbology in art and in Freemasonry and the various other secret societies.
Yesterday, my daughter took me to see the movie. I really wasn't expecting that I would enjoy it and neither was my daughter, but we both found it very entertaining. We both also found it quite stimulating in that it brought back in ways even more vivid than the book our curiosity in the works of art described in the book and shown in the movie.
One interesting aspect of my experience is this. When I read the book, it left me feeling betrayed by the church, or rather by my faith in the church. I didn't feel that yesterday, yet the movie seemed to accurately portray the book's story. I think it's because the book changed me, changed my perspective about Christianity and the Christian church. I had been teetering on the edge of this change for years, but reading the book sent me over the edge and I don't see that I'll ever get back the delusions that supported my faith.
If you haven't begun your truth quest yet, might I suggest that you go see this movie?