I agree, I think it's the contrast between how the characters are portrayed and the art style that makes me not like it as much. In the novel, the characters are very well written but in the manga it seems a bit watered down and the childish/cutesy art style doesn't suit it in my opinion. I think a more serious and dark art style would've did it justice, but that's just my opinion.
Anyway I recommend reading the novel if you're not satisfied with the manga.
Also, it would've also been good if the smut scenes were detailed according to the novel. Before I read the novel, the smut scenes here are acceptable for me as per restrictions but after reading it I think it was a waste. It was so beautifully detailed in the novel that it would have been nice to see it being drawn too for better imagination and feels
I read the novel long before the manga came out and you can only imagine how excited I was for it. However, I have to say that the manga rly doesn't do the novel justice, be it the general ambiance or the portrayal of the characters, including both the MC and ML. If you're looking for a more serious/mature, soft-spoken but firm portrayal of the MC, weathered and sharpened by her experiences as well as a ML with more depth (which some people in the comments seem to be dissatisfied with), I'd recommend going to the novel (complete). I really, really wanted to like the manga but as much as I tried to like it, idk if its the art style (example: big, anime-fied eyes, typical shoujo MC appearance) or expressions but I couldn't help being put off. Maybe it's kinda like how the book is always better than the movie? I'm not trying to diss the manga or offend anyone, but just some food for thought and a wholehearted recommendation to read the novel :) (=・ω・=)