I stayed speechless the whole movie, honestly it deserves at least an 8/10.
Split tells the story of a man diagnosed with dissociative personality disorder and who kidnaps three girls. The whole film is about the three girls getting to know which of the 23 personalities can help them escape, before the 24th appears.
James McAvoy’s performance is so impressive and shocking.  Honestly, playing 24 characters at once is so hard and I believe James was able to pull it off. Hands down. In general, the directing of this film was amazing [not only Kevin but also Casey, the two other girls and Dr. Fletcher].
Other than the acting, the cinematography and art direction is on point. I was impressed with the choice of shots, angles and framing, I thought each of one of the shots was studied to set a specific mood, to serve a specific purpose, it’s also the case for the art direction [Spoilers: the main colour theme in the flashbacks was orange, fall-ish colours whereas in the presence of Kevin, it was grey. Also, Casey only wore dark colours compared to the two other girls because she felt pain, as Kevin pointed out]. Thus, I found the movie visually satisfying and appealing.
The acting and visuals outweigh the story; I found the plot pretty basic, nothing extraordinary. In fact, if the main character did not have 23 personalities , the story would have been cliche and deja-vu. I did not like the ending scene because it’s a typical commercial ending scene; you know when they hint that they plan on to make a sequel and they present you a new character that supposedly will be important in the next film. Yeah, I was expecting something else as an ending scene so I was disappointed.
I highly advice you to watch it, it’s a very good film, not a waste of time or money.
+ By the way, I was stressed the whole film, it literally made me go crazy especially towards the climax. I love it when movies generate strong emotions.