Transforming a book from print to the big screen is a major untertaking. Sometimes it works and other times not so much. In my opinion, for Angels & Demons it helps if you did not read the book. You would probably not have the expectations (as I did) for something greater. That said, I think that for what it was (a Hollywood blockbuster) it succeeds.
Ewan McGregor lacks the charisma I expected from this role and Tom Hanks straddled the fence between intelligent professor and smart aleck, "I'm way smarter than you".
Good for what it was, check it out and judge for yourself.