If you're screenwriter Akiva Goldsman, it doesn't really matter. People keep giving him big paychecks even after Lost in Space, so he's clearly immune to failure. While minor details of the book have been changed, there aren't any surprises to the film, though Sony and director Ron Howard have done their damnedest to pretend that there are by being all secretive. As for the challenge of making puzzle-solving more visual, Goldsman has simply reached back to the template he employed for A Beautiful Mind. Like Russell Crowe's John Nash, Robert Langdon (Tom Hanks) visualizes mental puzzles via glorious 3-D special effects.
He is also similarly stalked by the annoying Paul Bettany, who plays Silas the evil monk, a religious fanatic who has taken a vow of austerity, yet carries around a cell phone and a gun arguably the most annoying inventions of the modern world. He binds his leg with a spiky metal chain in order to make it bleed, and he whips himself while saying his prayers. No denying that Bettany looks freaky in albino makeup. But then he opens his mouth, subjecting us to a ridiculous Dracula voice that undermines the scariness. Silas in the book passed for American at one point; alas, if you've seen Firewall, you know Bettany doesn't do American accents well either.
Silas isn't the main villain, though he commits the murder that gets the story going. He's merely the henchman of a faceless figure known as the Teacher, who seems to have deep connections within the Catholic Church and an animosity toward a secret society based in France called the Priory of Sion. (Author Dan Brown claimed to be accurate in his details about such a society, but it turned out to be a hoax; the movie claims that the hoax story is merely a smokescreen.) As the story begins, all four current leaders of the Priory have been killed, but the last one a Louvre curator named Saunière (Jean-Pierre Marielle), who took an exceptionally long time to die from a gunshot wound has managed to leave an elaborate cryptic clue as to the identity and motive of his killer. Part of it involves secret writing that mentions symbology professor Langdon by name; other relevant factors include managing to pose himself nude like a Leonardo Da Vinci drawing just before expiring (don't worry, the really bright spotlight aimed directly at his crotch manages to whiten out the naughty bits).
The dead guy's granddaughter is Sophie (Audrey Tautou), who also happens to be a cryptologist. Seeing the crime scene, she tries to help Langdon, but unfortunately for them, the chief police inspector (Jean Reno) is a hard-headed Catholic fundamentalist determined to pin the crime on Langdon. Chasing ensues, along with the emergence of other interested parties, among them creepy bank manager Vernet (Jurgen Prochnow) and a rather boring cardinal named Aringarosa (Alfred Molina). Most important, however, is Sir Leigh Teabing (Ian McKellen), an expert on the legends and history of the Holy Grail, which the Priory of Sion is believed to have guarded.
And here, for those who haven't been paying attention, is where the religious controversy begins. Part of the "history" revealed by Teabing includes the theory that Jesus and Mary Magdalene were married and had a child. However, given that the book obviously errs in minor claims like the word "Yahweh" being based on "Jehovah" (in fact, it's the other way around), it's clear that, while Brown may have been accurate in describing stuff he heard or read about, he didn't necessarily check the veracity of his sources. In a movie, it's less of a concern does anyone, for instance, believe that Indiana Jones really found the Lost Ark?
The faithful may be assuaged to hear that heresy has been played down. Langdon here is more of an advocate for faith, dismissing much of Teabing's scholarship as mere theory. This newfound faith also ties into the character's claustrophobia, which never really paid off in the book. (For what it's worth, such phobia can apparently be cured by having Audrey Tautou caress your face. Who'd have guessed?)
No, the biggest problem here is too much talk, despite worthy attempts to liven things up with full-on, big-budget historical re-creations of Isaac Newton's England, biblical times, the Crusades and Constantine's Rome. Once the Teacher is finally revealed (and there's a very limited number of possible identities) and defeated, the movie keeps going, mostly with theological babble that should have been covered earlier. The very final scene is nice, but the endless Rosslyn Chapel bit gets interminable.
All in all, a respectable and predictable adaptation.