TL;DR: If you are a Non Non Biyori fan, you have to watch this. If you hate slice of life anime, I don't recommend you to watch this.
I own and have read all the mangas up until volume 12 (which is the most recently released one) at the time of writing this review.
The manga itself is super good, but this movie made the contents even better than the manga. This is not saying the manga is terrible or anything, in fact it's one of my favorites, but the movie went in to much more depth for the vacation chapters.
It's been probably a year and a half since I read the chapters of the contents in this movie so my memories may not be 100% correct. I think most of the activities in the movies were done as like those "time-skip"/ "fast forward" panels where they just flash a scene and move on to the next in the manga, but this movie actually shows them doing these activities.
Just a typical slice of life story. Travel to Okinawa and do things there. Nothing much to say here.
I may be bias, but I'm a huge fan of Atto sensei's (original creator of NNB) and Silver Link's art style. The style is just like all the previous NNB anime. Oh, background art is beautiful as always. Really captures the nature. The animation is great too, I didn't see any bad animations watching it in the theatre.
No complaints on sounds either. Just like the previous NNB, they share similar style of music and BGM. I didn't hear anything that wasn't fitting. The OP is sang by nano.RIPE and still has the same chill and relaxing theme as the music they sang for NNB before. ED is sang by our 4 main girls and it's super cute!
This is why I love this show so much! Everyone is just so lovable! For this movie specifically, I felt that they focused on Natsumi the most out of everyone else. She got more screen time than any other character but not so much that it makes all other characters irrelevant. (Her screen time is cause of her relations and interactions with the new character that is introduced in this movie) You still get your super cute Renge and Koma-chan moments and oh, I found so many parts of the movie just making me and the audience around me in the theatre giggle. Pretty much all the comedic moments hit their marks. The character interaction is great as always! I found myself smiling so much during the movie and I can feel the joy in the theatre.
Having already read the manga, I knew what I should be expecting content wise, but after watching the movie I really felt like it blew the expectations off the roof. It was so much more than I could ask for and I would definitely go rewatch it again if I have the time for it! Gonna grab the BD for sure when they announce it!
This brings me back to my point in the beginning. If you are a NNB fan or a slice of life lover, you have to watch it. If you hate slice of life or has no interest in them, I really don't recommend watching this movie.