There’s nothing at all wrong with being young and naive, provided you plan to (and eventually do) grow out of that someday. As an occasionally critical reader, I find Dan Brown novels to be a step above the dime-a-dozen “romance” type novels. Less believable plots, less believable characters, more action and equally silly writing in general. But you like them, so that’s where we have to start. (I would have liked them, too, “once upon a time”, but I do try to read a bit more selectively now.)
I don’t know if you can get them on audio books—I don’t do those at all—but anything you can get by Tom Wolfe (The Right Stuff, Bonfire of the Vanities and A Man in Full are three that I recommend) or James Lee Burke (action / crime novels set in Louisiana, Texas and Montana, and a Civil War novel that I recall) are very good. These guys know how to use the language—and then demonstrate that knowledge. They also have a good eye for realistic (even if sometimes outrageous) characters.
Carl Hiaasen is very good, and you would probably enjoy Elmore Leonard (you’ve enjoyed movies based on his books, I’ll bet). Maybe even Patricia Cornwell.