I read The Da Vinci Code earlier this year, and found it to be a brisk read. Not high literature by any means, but a fun conspiracy story with just enough factual references to make it semi-plausible (at least with casual Internet fact-checking). I know people for whom it was a real test of faith, and others who saw it as something to be dismissed out of hand. I visited a Sunday School class that "debunked" the book. I found the teacher's use of the Bible as a proof-text entertaining - like creationists' using the Bible to debunk evolution - but, in the same manner, ultimately unhelpful.
While I attend a Methodist church and am raising my kids in that tradition, I am a skeptic about an active God, and would classify myself as mostly a Deist. I completely acknowledge the role of humans in writing, selecting, and editing the various texts in the Bible and other religious literature. So The Da Vinci Code presented no real "challenge" to my faith, such as it is. The book is enjoyable as a guilty pleasure. But I think a reader would get much more out of it if he or she were at least passingly acquainted with early Church history, especially the Gnostic movement and Constantine's Council of Nicaea.
Objectivism side note: I read in one of the Branden biographies that Ayn Rand had originally intended to include a Thomistic priest among the "strikers" in Atlas Shrugged, but deleted him out of concern that his inclusion would have been seen as an endorsement of religion. I would really like to have read that character's dialogue. I wonder if she destroyed the early drafts, though I doubt Peikoff would ever let the public see them.