The Outsiders, To Kill a Mockingbird, and The Perks of being a Wallflower.

I’d start out with classics.

Ursula Leguin’s Earthsea novels, and if the older one likes it, the dispossessed I read when I was like 13 was really good. I think the Earthsea series got a Turkish translation too if they prefer that (no idea how decent it is if it exists).

Fiction or non fiction?

I really liked the Ender’s Game series around that age. It’s weird, because while the author is a conservative Mormon, the books themselves have a message of tolerance and inter-cultural understanding.