his stories don't translate well to the big screen. Brown comes up with some good stories, but he's a horrible writer, his novels are choppy and poorly paced and he relies way too often on chapter cliffhangers to keep you 'hooked', like "...and then he opened the door and saw something that TOTALLY defied imagination and shook his beliefs to the core /CHAPTER" and then the next chapter is some completely unrelated ********.
I'd probably like most of the stories in Dan Brown novels if they were written by someone who had an actual understanding of history, an ear for dialogue and a knack for good pacing and tension building.
It also doesn't help that if you've read one Brown novel, you've pretty much read them all. They all follow the same formula meaning once you've read one of his books you can see the 'twist' coming a mile away in all the others (at least of the ones I've read, anyway).