@kelseyhusky
Yeah the only reference books I ever see anything like it it on are, like, giant dictionaries with the thumb holes. It makes finding the right section SO MUCH FASTER.
It’s weird, I used to never leave any marks in my books, now I just casually write in the margins and mark up the sides like this and write thoughts in the inside covers/flyleafs/etc. my relationship with books changed when I wasn’t looking.