I think he tends to follow them pretty well, but the trouble with Dan Brown isn't his technical writing; he breaks this unwritten rule: "don't make your story arc the same in every single book you publish."

I loved the first Dan Brown novel I read. I moderately enjoyed the second. Within 50 pages of the third, I knew exactly how the rest of the story would pan out and who was the hidden antagonist. Once you know the formula, the magic is gone.