People keep asking this and honestly, you can't go wrong with what's trending on TikTok, like Colleen Hoover or anything with a dark academia cover. But for actual high school popularity contests, I think it's a mix of those fast-paced romance series everyone passes around, plus a few old classics teachers keep pushing. 'The Hunger Games' had a huge comeback this year after the movie prequel came out – suddenly all the freshmen are reading it again.
In my kid's English class, they're actually assigning more contemporary stuff now, like 'Long Way Down' by Jason Reynolds. It's not the usual assigned book griping; kids seem to really talk about it. And for friend groups, the big fantasy series still dominate. 'Six of Crows' isn't new, but it's basically required social reading at this point. The real sleeper hit, though, seems to be graphic novels. 'Heartstopper' is everywhere – you see it in backpacks, libraries, you name it. It's less about the 'best' book and more about what gets shared between classes.