As long as you don't read too seriously into these books, they're good for entertainment reading. But man, this last one, as entertaining it is to see how Dan Brown takes all these loose threaded conspiracies to weave a "plausible" theory, there's only so many secrets Robert Langdon can help solve. He's the Jack Bauer for super secret societies and like 24, you can only save the world or uncover a twisted plot so many times before it becomes cliched.
I regret picking up this book. But I started it so I have to finish it.