To read aloud to teens (more specifics below)

My father calls my kids nearly every evening at 8 and reads out loud to them for twenty minutes. Over the years they've done plenty of classics, Treasure Island, Robinson Crusoe, the Spanish Bit Saga, Swallows and Amazons. They're doing Ursula K LeGuin now after finishing the rats of NIMH.

They need more suggestions. The kids on their own both gravitate to fantasy and sci-fi, but he prefers historical realistic fiction and I really want to support that.

14 year old boy and 16 year old girl, both love math and logic, biology and sports.

Can people please recommend to me some great books to read aloud, either classic or contemporary, ideally with some component of being exposed to a foreign culture or experience of invention/ discovery? Not fantasy, not horror, not self help. Male or female protagonist fine, age of protagonist unimportant. They're all mature enough to handle difficult content including complexity and human cruelty – the boy loved reading Dune, but that amount of sci fi turns my dad off.

I'd very much appreciate your recommendations, and please don't be shy explaining why you love a particular book!