Ansatsu Kyoushitsu: 365-nichi no Jikan is a compilation film of the Assassination Classroom TV series. While the film is mostly a compilation, I strongly advise that you finish the whole series before watching this. There's not much to say about the Art and Sound since it's almost the same with the TV Series. When it comes to enjoyment, I couldn't say that I "enjoyed" it since ninjas are cutting onions in the film. So here's the question: Should you watch it? Definitely. One thing worth noting is that the film have anime-only epilogue scenes. Unfortunately, many details were left out since the film only has around 90minutes of run time. I was also hoping for more epilogue scenes, or maybe some adapted scenes from Korotan D (search it if you don't know).
Nevertheless, it still managed to give an emotional impact especially for those who loved the series.