Fiction novel written in a Diary format where protagonist is Autistic/ Mentally Disabled.

[J]

When I was in 6th grade (2014-2015), I checked out a random book from the school library, something I pretended to read when the teacher was walking by. the cover art was a forest green colour with a black silhouetted person in the middle, which might've resembled one of those figures on bathroom signs. I could be mistaking that part for this copy of Me and Earl and the Dying Girl that I owned around the same time, but it was 100% a green cover. I can't remember the title but it was unusual and striking, like "I Did Something Bad". the narrator was autistic or mentally ill, and he spoke in a very disorganized and childlike way. something like:

"I go to school.

I like to go to school.

I go to school because it is where I have my friend.

I like my friend.

She is very nice to me."

I remember my teacher picking up the book and flipping through it like "wtf is this?"

it might've been written in journal entries. I barely followed the plot because I flipped through it half-asleep but the narrator did something insane near the end, something where all the other characters were furious with him, and he didn't seem to understand what he did wrong. and it ended on a really dark/sour note. I wish I had more detail but I was an idiot kid half-assing my reading. I've tried to find this book online just to understand what it was I read but I've never been able to. it's not The Perks of Being a Wallflower. Please let me know if you have any ideas.

[Sue]

Flowers For Algernon? https://www.goodreads.com/book/show/3...

[J]

Sue wrote: "Flowers For Algernon? https://www.goodreads.com/book/show/3..."

That's not the one, do you have any other guesses?

[Becca]

This Is What I Did by Ann Dee Ellis?

[Michele]

You might look at this list of books with autistic narrators:

https://www.goodreads.com/shelf/show/...