No offence to everyone else in this thread but the holy grail is truly The Art Of Problem Solving textbooks + mathacademy [0].
I learned way more reading crafting interpreters than I did in my compiler class for example.
But I also do read textbooks for fun… Now that I have a few decades of experience in a lot of these subjects I get way more out of the books. And I can start to understand more of the meta information. Like, of all the things the author could’ve used as an example, why did they pick that. Also, it’s hugely interesting for me to look at the homework problems and theorize why this particular problem was picked. Especially fun for electrical engineering books. But ya, I’m weird like that.