As many others said this is a recap movie, however, i would like to add a lot of people who said there wasnt much new scenes is greatly mistaken. Sure it didnt make a huge impact but there are quite a few extra scenes that wasnt in the anime. ** Spoiler Alert ** In the beginning there was the dive scene. Momonga chatting with Sebas was modified a bit. Lots of pan out scenery shots of the cities and Nazarick. The slane theocracy mission. And a few more.** End Spoiler **

Again it doesnt make a huge impact if you did watch the anime but it does add a little bit extra details here and there, which i enjoyed watching (despite watching the anime a few times and having it rather fresh in my memory).