In responding to Cathleens question below, I have to say that Im not really mystified why DVC is so popular. I hear the writing is bad, but anyone who thinks that is a barrier to popularity hasnt been reading the best seller lists lately. I myself am currently enjoying a series of badly written murder mystery novels that involve card cheats, wise guys, and a retired police detective (But then, I grew up in New Jersey;-). DVC has also been exceptionally well-marketed.
But its true that other novels with these kind of themes have not done as well as DVC. Holy Blood, Holy Grail never became the cultural event that DVC has, although it did sell a fair number of copies. Robert Ludlums Gemini Contenders (yes, I do read a lot of bad fiction, why do you ask?) was about a scrap of parchment concealed by the Church that had the disciples saving Jesus from the cross at the last minute and then covering it up.
The fact that the United States is a Christian nation is certainly no barrier to lurid fiction that depicts the Catholic Church in a bad light. There is a real tradition of that, too, going back to The Awful Disclosures of Maria Monk, a fictional account of a woman imprisoned in the Hotel Dieu convent in Montreal in the 19th century.
I think that Cathleen is right that this is sort of a perfect storm situation, where the loss in credibility suffered by the Church as a result of the scandal interacts with popular (and often inaccurate) depictions of the diversity of beliefs about Jesus in the 2nd century. Throw in an enterprising writer and an well-oiled marketing machine and you have the makings of a real cultural moment.
But the widespread popularity of the book doesnt keep me up nights, nor do polls suggesting that people believe that what the book says about Jesus is true. Its like the polls that tell us that a majority of the American people believe in UFOs. Is it a deep belief, or just a random response to a pollster? Is this a belief on which you are willing to bet your life?
Now I should say that those who are concerned about the tone of some of the anti-DVC material out there should go back and read Irenaeus, Tertullian or Athanasius. These guys didnt exactly pull their punches either. Come to think of it, I think that Jesus may even have uttered a harsh word once or twice during his ministry. So Im sympathetic to those who feel a need to set the record straight. The tendency of far too many to throw up their hands and say we cant really know what happened isnt a sign of healthy skepticism. Its a pathology.
But I think the anxiety that lies behind some of the anti-DVC apologetics is a more general concern about a decline in what might be called religious literacy among the Christian faithful. That DVC is full of nonsense should be obvious to anyone with a rudimentary knowledge of the origins of Christianity. I think that aspect of catechesis has been neglected and is something we need to work harder at in the future.