Why didn't I read this before it's getting anime adaptation... Should I read this?

u should def read it, but also depends if u first want to watch the adaptaion (since it's getting adapted rlly good so far, it might be interesting to start by this)

absolutely the manga imo has more depth to it and portrays their emotions and aspects of their relationship better!

Honestly you don't have to, you already have an anime, so... It's not much different