Which books are the original Webnovel?

I'm sure this question has been asked numerous times (so sorry lol) but I've been trying to research as much as possible beforehand and I'm still confused a bit so I'll have to ask here!

So I heard the Webnovel has 551 chapters, is it just a plain text kind of book? There's many copies such as some on Amazon, but they all seem to have pictures and I'm unsure what is what. I thought it was a text only kind of thing? What's the original 551 chaptered Webnovel to read first? Or is it not released yet?

Lots of different kinds of stuff is out there so I'm unsure how to find the original Webnovel before trying the Webtoon.

Hopefully you guys can help me out! Really want to read this one! Thanks <3