I think this is a great movie in almost all aspects.  To start, the overall story interwoven with the real-life mystery of the Zodiac Killer is masterful, and it's surprising that this was a story based on true events.  The characters are well 'written' and definitely well acted, with Jake Gyllenhall's character being a standout.  While a lot of the characters were really bland, he was great and thankfully he was also the lead.  The drama aspect of the movie is alright, but this is definitely more of a mystery/thriller than a dramatic film, not to say that there isn't good drama here.  The visual style is consistently good, just like Fincher's other films.  Nothing to really complain about here, but doesn't quite reach the heights of other mystery movies (that aren't based on true events).