The first 15 chapters or so are just primo bait for anyone that wants to feel like committing physical violence upon fictional characters. Like, the book's male leads suck real hard. The author knows this and exploits it pretty well and the story continues moving towards the heroine's goals. We meet the Male Lead (proper), the protagonist gets harrassed by the book's male leads who eventually start simping for her etc. If this seems like a pretty dry description of events, that's because this work is mostly carried by how well you deal with somewhat cringey humor. I don't mind it personally.
We meet the book's heroine, who has meta-knowledge of the book's universe from having retained her memories of an indefinite number of story cycles stated to be the number of times the book has been read, which is enough repetitions for her to have gained severe trauma from constant exposure to the events of a trashy harem novel's plot. That isn't me editorializing either, they really do play every male lead in the book straight, and these boys are messed up. Our protagonist and the heroine team up after some convenient contrivances as it's pretty clear that the heroine also wants nothing to do with the events of the story. You do get to see the protagonist rip apart those annoying male leads from earlier which is nice, and she has to think up plans to outsmart arrogant teenage boys. I'd say this is about where it peaks.
Throughout all of these events, our protagonist has been learning the sword and this turns into a battle manga. It's not good at being a battle manga, but the fights aren't too drawn out. There's no unnecessary theory to it either, she just jacks an endgame (isn't this a book?) sword using her protagonist powers of having read the book. She's also just Good At Sword canonically or something. From this point on, our protagonist beats her problems to death. Also her softboy puppy husband gets powered up as well but he's... like....
If you've made it to this point, congratulations. Let's talk about Nine. Nine is the name of the Male Lead, he's a blue dogboy and the softest sweetboy I've ever seen in this genre. The man is cute. He's 6 foot 2 of pure moe. The problem is that he's so incredibly passive that when the author of this webtoon decided her protagonist was going to be as dense as the average genre protagonist, this created a scenario where these two just.... don't have good chemistry. Like, their relationship is fine and believable but there's just no spice to it. It doesn't do anything for me. Nine doesn't really have a personality, and the protagonist's personality is mostly doing visual gags for the audience. This is really what makes it a battle manhwa more than anything else, the main relationship is kind of sterile, it feels like it gets its obligatory chapters just to space out the next battle.
So basically the protagonist beats everything up to the end, where we get a brief twist before she beats up the thing and the story "ends", which for this kind of webtoon means like 30 more bonus chapters. In keeping with the theme of this work, they're a mixed bag. I really liked Yona's sidestory and Nine's backstory was ok, but made me think that the series would have benefitted if it started here rather than with the protagonist. It's got a ton of characterization for Nine who is otherwise a wallflower.
This one's really hard to appreciate on both of its entirely seperate merits. It's an otome villainess isekai with a boring main couple. It's a fantasy battle isekai with no sense of the protagonist's capabilities aside from them just doing everything and making it out okay. The only thing tying these two ends of the story together is the humor, which is not particularly special itself. I liked the side characters but some (Kartena/Robbie) got way more screentime than others, to the point where I got pretty bored of seeing them. I'm really glad Yona got a proper backstory, that made reading all the way past the ending worthwhile, although that of course had to end so we could get more of Robbie and Kartena. And of course baby Nine.