Split was nonetheless ignored by the Oscars and BAFTA, but various festivals did recognize the movie, particularly James McAvoy in his demanding multiple personality role.
Today at imdb.com, the film has a huge 516K user votes, and the user ratings are fairly high at 7.3 out of 10. The user reviews tend to be written by cinephiles who have seen many Shyamalan movies and are divided on whether they are getting better or worse. Of course, the one Shyamalan movie everyone seems to love was made some years ago, The Sixth Sense back in 1999.
How I felt about it. There are minor things about this movie that I don't like. The connection to Unbreakable seems dubious. It seems to me that Shyamalan finished the film and it had promise as a commercial success, so, in The Silence of the Lambs style, a sequel was in order. This meant keeping Kevin alive and free.
Shyamalan thought about what the sequel might be, and decided he could blend it in with Unbreakable. Thus Glass is a sequel to both films, but Unbreakable and Split are different movies with different plots and different characters, save for the needless Bruce Willis cameo at the very end of the movie. Which could have been filmed at a later time, once the sequel was plotted.
Certainly, Split has much in common with The Silence of the Lambs, which also had a teenage girl held captive by a disturbed man who plans to murder her for reasons other than sexual gratification. It also has a plot climax similar to so many horror movies, in which a deranged older male killer pursues the teenage girl victim in an isolated setting. Usually in such films, she kills him, but in this movie they both get away, ideal for the sequel starring both the actor and actress.
The premise of Split is that if a personality believes something about his own body with enough conviction, it becomes true. If you think you are a beast, you become one. There are psychosomatic disorders, but this movie takes things to a preposterous extreme. Otherwise, hypnotists could cure cancer patients. Good luck with that one.
We do feel sorry for Casey. Not only because she is being held prisoner by a madman, but also because her guardian is a detested and abusive uncle. At least she has her big, beautiful eyes going for her.
On the whole, though, Split is a really good movie, one that confirms that it can work well when the director is also the sole screenwriter. The vision of both roles is unified.