Hmmm..

After taking it to court, the judge ruled that no, he did not in fact rip off "Holy Blood, Holy Grail." While they cover indubitably similar topics, I'd say Derek's statement of it just being a general formula of "conspiracies" and "esoteric groups," as the specifics in question, have been tossed around for ages. As far as literature is concerned, theirs was equally fiction, but Dan Brown's "dumbing it down" and selling millions made them a tad jealous.
 
Indeed, that was the central tenet.

I can't argue that Brown creates a page turner, I just question the value of his flaccid prose. :)