I'm a big fan of David Fincher and the photography and atmosphere is above expectations. But...:

this film is so boring and so pointless that the audience is carried for 150 minutes only because they started watching and want to see how it ends. You're going to be disappointed.

More sophisticated people will tell you that this is a master piece with tension and atmosphere and crude but simple violence. Just because a film peace is sloooow doesn't mean it's a good film.

So many times you think you're close to solve the enigma and this sad plot works for those who doesn't know the (real) story of the Zodiac that is depicted in this film.

Trust me: spare you a lot of time and go on Wikipedia to read the Zodiac story which is complex and chilling without the need of a dramatization of a pointless 2 ad a half hours.