from someone who read the webtoon (didn't read all but the most):
I recommend it for the ones who read or didn't because it's reaaaally good.
I watched without noticing the "real context" of the story BUT at the end my mind could connect the story of the drama with the webtoon and realized that the drama is before the start of the webtoon.
so... the adaptation is really good and is beyond my expectatives.
the acting, music and story are all really good in general and because they "started from before" everyone can just watch it and be in equal aknowledge (about the actual story) with the ones who read it.