Help! I was asked for recommendations for my younger cousin and she went way more nuanced than I expected.

She wants a good sci-fi book "in which the world affects the characters perspective as a person".

She's YA/Preteen so nothing too insane, but she normally reads pretty advanced for her age.

Edit: Thank you all so much for all the recommendations! You've given some great options and reminded me of some from my childhood as well!