I feel that a comparison between Harry Potter and Dan Brown is unfair. That's because Harry Potter is good, and easy to read because it's written also for kids. Dan Brown is cotton candy for your brain. It tastes good at the time, it's not especially filling, you plow through it quick, but you're also not going to eat it more than once a year.

for lit types, this is how I sum up reading the Dan Brown:
"Little did he know that in less than sixteen hours, that piece of information would save his life." (Paraphrased from the third or fourth chapter Angel & Demons, but a similar phrase appears in the DaVinci Code, as well)

That said, I liked Angel & Demons much better than the DaVinci Code, it's got more to chew on, even though both sort of feel like what happens when they turn a movie into a book.