It honestly becomes a much more philosophical series after that. No more action or Ender just being better than everyone else for plot purposes.
My personal favourite is Speaker for the Dead, the direct sequel to the original.
As a quick summary, I'd say that book 1 is like a teenager while books 2-4 feel like old men. Not sure if that makes sense to anyone but me though lol.
There's some crazy amount of books out there all told, and you can pick and choose which little duologies/trilogies/quartets you want to pick up within the greater universe depending on what style you're looking for.
The biggest knock against those books for me is that the author is, unfortunately, a piece of shit.