Everything that I said for Angels & Demons applies to The Da Vinci Code as well. I will, however, admit that Dan Brown's writing has noticeably improved between the two books. For that reason alone, if you somehow have to read one of the two, I'd probably recommend this one. But you're better off not reading either of them.
It would not be nearly half as bad if Dan Brown just did one thing: throw out that stupid "fact" preface. One reviewer explains it far better than I can: this is worse than a fluffy beach read, because beach reads don't insist that their conspiracy theory fiction is fact. The Priory of Sion was founded in 1956, not 1099. The history of Christianity, history of the Bible, and etymology of the Holy Grail are far more complicated than Dan Brown makes it seem, and at some points, he blatantly misrepresents the history of the Church. Once again, it's not the nature of these fabrications: fiction is good. But fiction claimed to be fact does no favours.
I think I'm done with Grail myths and Templar fiction. Time for some fresh conspiracy theories.