I decided to watch this film after reading other people’s opinions, and I must say I wasn’t impressed at all. In my view, M. Night Shyamalan’s last genuinely successful movie was The Village, because he seemed to have a firm grasp of his own directorial approach then. With Split, he appears to be attempting a similar method, but the result falls short. There wasn't any effective development or unveiling of the story, and when the credits rolled, I just felt like saying, "That’s all there is?". The performances from the cast were fine, certainly, but that didn't improve my overall impression.

Source on TMDB