They keep you wanting to turn the page! (And I don't mean to hurry up and finish the darn books.
) The book that got the pages turning most, was probably Deception Point
I'm under no illusions about the fact he's not the best writer or his claims aren't so true, and that doesn't effect my enjoyment for what they are, just exciting fictional works.
One can debate his theories about Leonardo's paintings and so on, yet his books are under fiction, so you don't have to get too serious about it all. The books can be samey in the way some characters behave and all that, but yeah, if it's keeping me interested, then never mind! One thing that bothers me more is that SLIGHT SPOILER
the main character Robert seems to have some kind of relationship with every girl he has been on these 'adventures' with. Really? Again?
And then they have disappeared from mention by the next book. Dan Brown seems to see them as standalone books, but it's not too unreasonable for the character Robert to see links in all these chases that are occurring: 'Ah, not another chase with my life being in danger!'.