Great movie. Made for the old Kuroshitsuji fans - otherwise you will not get it too much - it is one of the best movies of the saga. Although my first impression was that it was going to be another story like any other, it had two main highlights: good story and, specially, great character development, e.g. we get a deeper look into some of our favorite characters, and that was for me the best part.
Fun, quick, with a lot of action and good fights, it is a must for any Kuroshitsuji fan (you probably need to have seen at least first season).