Is the film Se7en horrible?

The film Se7en with Morgan Freeman and Brad Pitt, is it horrible? I mean im 14 (and i know its an 18 but im just asking) i asked my mum if we could get it, and normally she's ok with getting films i mean she's bought me Reservoir Dogs, Pulp Fiction, Taken and films like that in the past. I just wondered what could be so terrible in this film that she would interrupt me with 'No, no that's a horrible film, your not having that.' before i had even finished asking her for it?