It turned out a lot of the "factual material" he wrote in turned out to be wrong anyway. So it's a made-up story loosely based on made-up facts. That's not necessarily a deal breaker except that the idiot author can't get his story straight on how accurate his book is. Though he does get more free press the more controversial it/he is.
Unfortunately, none of that changes how friggin' boring the whole premise is. A conspiracy theory involving the Catholic church? Wow, fasten your seatbelts.
Since we know this movie, like every other summer movie, is just a bunch of nonsense anyway, why not go for the summer movies where cool things actually happen? At least in MI3, we got to see Philip Seymour Hoffman implant little explosive devices in people's heads and then detonante them (resulting in a cool lazy eye effect that grossed out the girls in the crowd), and Tom Cruise shot down an airplane with a machine gun. And lots of other stuff exploded. And there was a helicopter chase. And a long action sequence in Shanghai.
Or you could watch Tom Hanks pretend to unlock some secret code about the Church that everyone already knows about thanks to all the stupid hype.