M. Night Shyamalan is a mysterious creative force. Bold statement, I know! But through his love of the mediums of film and comics, he's created a trilogy spanning nearly 20 years that was essentially a complete surprise. The landing sticks, but a lot of the emotion of the third film, Glass, is lost in the process.
One of the reasons why Unbreakable and Split work so well is because they're standalone films. No prior knowledge of anything, even a vague notion of comic book history, is required to enjoy them. But with Glass, so much setup is required (like, say, watching the two aforementioned entries) that Shyamalan is essentially forced to spend a lot of its runtime waxing poetic and exposition, which significantly hurts the flow.
Glass is a comic book epic filmed on a shoestring budget and Shyamalan makes it work. The purple, yellow and green motifs, all signifying Samuel L. Jackson's Mr. Glass, James McAvoy's Kevin/Horde and Bruce Willis' David Dun/Overseer personas are peppered throughout, providing an aesthetically pleasing backdrop to all of the (mostly) single-setting chaos.
Shyamalan gets down to business after a quick token cameo: David and Kevin, both capable of superhuman feats, go at it almost instantaneously, then are thrust into Raven Hill Memorial for treatment. There, Dr. Ellie Staple (the always reliable Sarah Paulson) tries to convince them they're not "super." It's a far cry from what most people expected, and would work as a decent setup, if not for a few questionable decisions and makeshift editing.
My chief complaint is that for a trilogy kicked off by a Bruce Willis film, Willis sure isn't present all that often. I'm not just talking about literal screen time either: Willis seems like a ghost of his former self in Glass, coasting by with a far off look in his eyes, miles apart from the talents of the rest of the cast. We know he can effectively play David Dunn, we've already seen it. But it's not just a case of "not having the material," Willis proves that he wasn't willing to rise to the occasion.
James McAvoy once again puts on a clinic with his myriad personalities, but Jackson's quiet brooding performance as Mr. Glass also warrants further rumination. By the time everything comes together you really start to understand these characters (with the exception of Dunn) and the world that Shyamalan has created. In the end it's just enough to cement itself as a successful trilogy in spite of its faults. For that, Glass owes a great deal of debt to its predecessors for making it look presentable.