This is a feminist movie. What kind of image does it conjure up for you?
I can tell you that this isn't a story about a confident, "girl crush" woman. Rather, it follows the story of an ordinary woman and the gender based microaggressions she faces.

This movie isn't an easy watch precisely because it's so real (similar to Misaeng). You could only hope that all of those events don't happen to the same person in real life though.

I knew about the general plot before watching the movie but it still really hit me hard. At the start, I thought it was really fast-paced because it just threw you into the movie. But as the movie progressed, I got used to it and was able to connect with it more.

However, I think reading the book would help you understand the movie better. There was a few scenes that didn't feel resolved in the movie, but I think were explored in the book.
I was also confused if Kim Ji Young's behavior was supposed to be more metaphorical or literal. After reading some reviews of the book, I think I understand what it's trying to say. There was one review in particular that said she didn't have a voice in this society so she had to adopt other personas / mimic other people in her life to say something.