Now, what I mean by that is that the book succeeded, as a book much better than the movie succeeded as a movie. That is really the only way to compare these types of "apples" and "oranges". I don't know what it is about Dan Brown, but none of the adaptations of his books has been very good - in fact, I think they have declined steadily until we get this mess.
Basic plot is that Robert Langdon wakes up in Florence, Italy, the victim of an apparent gunshot which grazed his skull. If you know Brown, then you know what evolves from there is an Intellecto-cutural scavenger hunt that masquerades as a travel log of Italy and, well, let's face it a six hundred page (or two hours plus) demonstration of how fricking much more about any of these topics Brown knows than us. He is, as someone once called it, a super smarty pants, and boy does he show it.
The problem with Ron Howard's film is that it fails, almost from the beginning to track Brown's relatively intricate plotting and character development, and just assumes that steadicam shots of havoc and mayhem in beautiful Italian locales will suffice.
Well, they don't.
And nearly no one in this film is well cast, including, I am sorry to say Tom Hanks. While he is a good Langford, he is not a good badly written Langford, and Felicity Jones never sinks her teeth into the robust material supporting her very interesting character. Or, again, maybe she is just suffering from a sub-par script form the usually dependable David Koepp. And Omar Sy as the possibly double-dealing WHO scientist-cum-agent-cum-well whatever? The only thing interesting about Sy's character is that he briefly swears in French, and Jones briefly responds, showing a tiny bit of the depth of her otherwise impenetrable character.