Where side character's early in the book use certain phrases. Which on the first read you'd probably not even take note of, but on the second realise who they're quoting and the implications that have. Details that at first is just there to give a picture but say more when you know what it means.
(eg. "The greater good" doesn't mean much more than that, but in a HP fanfic…)
Something with good rereadability. Almost a different story the second time you read it.
I'd also be interested in something with somewhat murky morality. I'm currently more inclined to something fantasy but it's not necessary. Something more character focused, with large events in the background, though with a few small actions they may (unintentionally or intentionally) kickstart larger consequences.
I'd also be interested in something where one character owns controversial or banned literature that might get them in very serious trouble should people find out.
Something without romance, or where romance is not the main point please.
by Specific_Ad3112