Okay, so let’s agree that Dan Brown’s “The Da Vinci Code” is a cruddy potboiler that’s laughably loose with facts in cobbling together an avalanche of goofy theories from past “researchers” to concoct an absurd, and in the final analysis, ludicrous thriller scenario involving a vast ecclesiastic conspiracy to suppress the truth about Jesus and his relationship with Mary Magdalene. A cottage industry has arisen of commentators, both anguished amateurs and smirking scholars, who have pointed out the historical howlers and supposed blasphemies that undergird the tangled plot.

But that all doesn’t change the reality that the book has become one of the most successful in modern publishing history, or that however ridiculous the tale may be (and however uninspired the writing), it’s captured the imagination of millions upon millions of readers. It was inevitable that there would be a big-budget Hollywood attempt to tempt all those fans into theatres to see if the labyrinthine, provocative tome could be successfully transferred onto celluloid. No expense has been spared; when you have Ron Howard and Tom Hanks on either side of the camera, jet off to some sumptuous European locales for authenticity’s sake, and add the likes of Ian McKellen, Audrey Tautou and Paul Bettany to the cast to give it a further sheen, you’ve talking about a seriously funded project.

The result, of course, can’t be any better than Brown’s book from a narrative standpoint–readers wouldn’t appreciate a movie that deviates much from the original any more than those of “Gone With the Wind” would have done back in 1939. The issue isn’t whether the moviemakers have been “faithful”–they could hardly have been otherwise, and the alterations they’ve made are actually quite modest–but whether they’ve managed to turn the convoluted, protracted and ultimately dumb story into a picture that works as an exciting if vacuous chase movie, like most readers felt the book did.

The answer is, unhappily, no. Akiva Goldsman’s script has necessarily streamlined things–dogged adherence to the book would have required a miniseries (which, actually, might have been preferable)–but he has included all of the main episodes, and uses fuzzy flashbacks as a sort of shorthand to cram in bits and pieces he couldn’t cover at length. He’s forced into increasing compression in the later going, though he engages in some expansion there too in any effort to clarify dangling plot threads and added some twists to the penultimate “chapter” that will surprise (and perhaps irritate) Brown devotees. (He’s added a few throwaway bits that soften the blanket indictment of the Vatican and Opus Dei, as well–although one of the excisions, maybe as a result of the accession of Benedict XVI, involves Brown’s stuff about a “liberal” pope clamping down on the prelature.) Goldsman (and director Howard) also downplay the romantic angle between Hanks, as Harvard symbologist prof Robert Langton (the Hitchcockian “wrong man” of the plot) and Tautou as pretty policewoman Sophie Neveau, whose personal relationship with murder victim Jacques Sauniere (Jean-Pierre Marielle) leads her to assist the American to unravel the secret behind his death–an effort that takes them into a frantic search for “the Holy Grail.” One can understand this omission from the perspective of running-time, but it does make the characters much less interesting than they might have been. (Of course, it’s possible the two stars just lack a chemistry they’re supposed to have.)

And the screenplay, however cannily managed, can’t disguise the fact that despite all the chasing about, thrashing around and globe-trotting, Brown’s book is a very talky one, filled with reams of heavy-handed exposition, cryptic cryptology and wild-eyed theorizing. On the page the eye can dispose of all the blather reasonably quickly, but on the screen, however briskly declaimed, it grows very wearisome, and–from the perspective of the uninitiated–probably more than a mite confusing. Howard tries to relieve the verbosity problem by inserting elaborate period recreations into the lengthy monologues as visual ornaments (scenes of the Council of Nicaea, of the First Crusade, of medieval knights in battle, of the slaughter of the Templars in 1307, and of a completely made-up religious civil war that was supposedly going on the fourth-century Rome–among others), but oddly they only make the movie look like out-takes from a bad History Channel documentary. So there’s a lot of movement in the movie, but it’s definitely overloaded with long-winded dialogue that makes it feel terribly sluggish (and though Hans Zimmer’s score tries to rev up the energy, all it really increases is the decibel level).

And the acting could have used a bit of panache. Howard has loaded his cast with consequential people–Hanks, Tautou, Bettany (as the scary albino Opus Dei “monk” Silas), Jean Reno (as police captain Bezu Fache), Alfred Molina (as Opus Dei Bishop Aringarosa), and Jurgen Prochnow (as bank exec Andre Vernet)–but their performances are no more than serviceable, as they’re forced to plod through the plot convolutions and mouth their speeches without ever raising their characters beyond the cardboard figures Brown presented on the page. The only person who really throws caution to the winds and runs with the loony material is McKellen, as the flamboyant Sir Leigh Teabing. His dialogue is hooey and his character a thoroughly wacked-out eccentric, but McKellen relishes the nonsensical quality of the role, and goes all the way with it. Watching him provides almost the only fun the movie affords–apart from the locations, most of which are caught with finesse by cinematographer Salvatore Totino.

But elegance, seriousness and sobriety aren’t really what “The Da Vinci Code” required. For this story to have succeeded on screen, it needed to be told in a flashy, trashy, lowbrow style which is no longer in Howard’s repertoire (if it ever was). So what’s really a ridiculous potboiler–a treasure hunt movie that isn’t much more than a modern version of “Raiders of the Lost Ark”–is played as though it possessed almost Shakespearean heft. I suspect that those who haven’t read Brown’s book will find it, if not exactly incomprehensible, boringly complicated and turgid. As for those who have read and enjoyed the tome, they’ll likely react like the “Star Wars” devotees who instinctively praised the last three installments when they initially appeared and then slowly admitted how bad they actually were. It doesn’t take a great code-breaker to decipher the fact that for all the elaborate theorizing and running about in it, this movie is awfully empty-headed and flat-footed.