For historical fiction, as a particular genre, to be credible the underlying facts have to have some semblence of accuracy. Nobody expects that every detail to exact, every character to have existed, and line of dialogue to have been spoken, etc. But Brown bungles the facts of history so badly that it's funny. In fact, when I read how Daniel Henniger, in last Friday's Wall Street Journal summed it up I was laughing so hard I'm sure people in the office were looking at me:
The real accomplishment of "The Da Vinci Code" is that Dan Brown has proven that the theory of conspiracy theories is totally elastic, it has no limits. The genre's future is limitless, with the following obvious plots:Bill Clinton is directly descended from Henry VIII; Hillary is his third cousin. Jack Ruby was Ronald Reagan's half-brother. Dick Cheney has been dead for five years; the vice president is a clone created by Halliburton in 1998. The Laffer Curve is the secret sign of the Carlyle Group. Michael Moore is the founder of the Carlyle Group, which started World War I. The New York Times is secretly run by the Rosicrucians (this is revealed on the first page of Chapter 47 of "The Da Vinci Code" if you look at the 23rd line through a kaleidoscope). Jacques Chirac is descended from Judas.
Cordially,