Critical Thinking Question: How different are people allowed to be in this text?

In the book "The Perks of Being a Wallflower", I feel like the main character Charlie distances himself from other people. He mostly stays silent and just thinks to himself a lot. A 'wallflower' is a term that one of the other characters used to describe him.
Charlie eventually meets Sam and Patrick who also seem very different, and Charlie starts hanging out with them. He seems to be very excited by having new friends and experiencing new things with them. It seems as though, to me, that how different Charlie is to the rest of his school is very much accepted by everyone and especially his new group of friends, seeing as though they're pretty different too. "You see things. You keep quiet about them. And you understand." I think that this shows a lot about Charlie as a person, and I also think this has a lot to do with how the people are grouped in the book because Charlie’s group or kind of people seem to just observe and take in whereas other people would want to be outgoing and put themselves out there.
I also notice that this book is written a lot like if you were to just put all your thoughts on paper, or as if you were saying them out-loud. I suppose this is Charlie's way of actually getting his thoughts out, not really having the format matter since he doesn't talk much when he's around people.
I think that being different and trying or learning about new things is a big topic in the book. And the way that Charlie's character develops through the story with Sam and Patrick's help is really great. It kind of also teaches a lesson about how friends can change you in a good way.