Honestly Harry Potter was the last big one that came to mind. In the time it took for the Potter train to slow, streaming services and personal devices came up in a big way.

Its possible that HP might be the last big book series to have that kind of impact.

Slightly less ‘fantasy book’ and more ‘fantasy comic’ but Amulet by Kazu Kibuishi is a fantastic and building story over 9 novels. My 6 year old loves them and I’ve enjoyed reading along too

I’m not sure which generations are post-Harry Potter but my sister is 12 and her big children fantasy book was… Harry Potter

I think Percy Jackson is a huge thing