u/alocalbuffoon

I looked through my bookshelf and saw this. Is this book called, or is it just a stain? In case it was book mold I put it in the freezer, but I’m still nervous. Is this book mold? If so, is it good to put on my shelf now that it was in the freezer? I’m not sure what to do. I went ahead and reorganized my bookshelf just in case.

Note: the reason I think it could be book mold is because I live in a humid climate and saw a few TikToks about it.