Harry Potter was a smash hit about a boy discovering he’s a wizard and going to school in a magical world full of wonder and adventure. Twilight didn’t hit quite that high a note, but the story of a teenage girl who learns her classmate is a vampire and falls in love with him did quite well. The Hunger Games popularized the dystopian genre with a bow wielding teenager stepping up to survive death games, have angsty romances, and fight the power.
As far as I can tell, nothing has quite hit that same kind of high since and it may be awhile until the next truly big wave. But if it were up to you, what would the next big thing be about?
The world is more fleshed out, the magic system is more clearly defined, the characters are nuanced, the stakes feel more real…
Lots of things are cultural phenomenons, that doesn’t mean they’re the summum of quality in their genre. Harry Potter was the birth of YA, but since it has been written, much better books have been published - Scholomance trilogy among them.