If you haven't watched the movie
Angels & Demons yet, I'd really recommend that you read the
book first. As always with most novel/book turned Hollywood movie, this one ommits and cut a lot of details and plot to cramp into it's 2 hours storyline. The book is okay but the movie kinda sucks.
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A word of advice though, if you're not really into ancient history I'd give this movie a miss. Angels & Demons the movie is a real snorefest. Heck I didn't even finished watching this one (at home of course).