I’ve done a little browsing of booktok and seen lots of young adult novel recommendations, but many of them don’t specify the age group, which can be an issue. Take ‘Icebreaker’ for example, I’ve always seen it described as a romance by adults recommending it, and then it took a while before I got a video on my for you page of a teenager stating how shocked they were when they discovered how mature the book really is. I haven’t read it myself, but apparently there’s some parts with strong sexual themes, and if you look at the cover it looks like something aimed at young teenagers.
I’m going to go with either Tess of the d’Urbervilles because it’s my favourite or Vanity Fair because it’s also good and incredibly long