An old interview about the novel:
Q: Isn't "The Da Vinci Code" just a work of fiction? Why do you think it was important to write a book like yours?
Welborn: "The Da Vinci Code" certainly is a work of fiction -- in more ways than one, actually. But within the framework of this novel, author Dan Brown presents many assertions about history, religion and art. He presents them as truth, not as part of his fictional world.
For example, one of Brown's central points is that the earliest Christians did not believe that Jesus was divine, and that Jesus and Mary Magdalene were married.
He puts these assertions in the mouths of scholar characters, and frames them with phrases like "Historians say" and "Scholars understand." In addition, Brown presents the titles of real, albeit unreliable, sources within his book, as well as in a bibliography offered on his Web site.
Further, author Dan Brown has repeatedly said in interviews that part of what he is doing in this book is presenting a heretofore "lost history" to readers, and that he is glad to be doing so.
So, certainly, "The Da Vinci Code" is a novel, but the author makes assertions about history within the novel, presents them as fact and widely accepted, and it is this element of the novel that has disturbed some readers and requires a response.