Since you stick to the notion that Dan Brown claimed that the story is true, here is what he says on his own website about the DaVinci Code in response to specific questions:
Q: HOW MUCH OF THIS NOVEL IS TRUE?
A: The Da Vinci Code is a novel and therefore a work of fiction. While the book’s characters and their actions are obviously not real, the artwork, architecture, documents, and secret rituals depicted in this novel all exist (for example, Leonardo Da Vinci’s paintings, the Gnostic Gospels, Hieros Gamos, etc.). These real elements are interpreted and debated by fictional characters. While it is my belief that some of the theories discussed by these characters may have merit, each individual reader must explore these characters’ viewpoints and come to his or her own interpretations. My hope in writing this novel was that the story would serve as a catalyst and a springboard for people to discuss the important topics of faith, religion, and history.
Q: BUT DOESN’T THE NOVEL’S “FACT” PAGE CLAIM THAT EVERY SINGLE WORD IN THIS NOVEL IS HISTORICALLY FACT?
A: If you read the “FACT” page, you will see it clearly states that the documents, rituals, organization, artwork, and architecture in the novel all exist. The “FACT” page makes no statement whatsoever about any of the ancient theories discussed by fictional characters. Interpreting those ideas is left to the reader.
Your turn.
Good volley. I have not read his website. The "FACT" page in his book is cunningly worded and without reading the website one does come to the conclusion that I and most others have -- that the author was claiming that everything including the belief that Jesus had kids was true.
One key element, the Priory of Sion which Brown claims as fact. for one example, is a debunked fraud.