[gonehome]

I really loved this book: https://www.amazon.com/Code-Language-Computer-Hardware-Softw...

Which goes from bits on up without shying away from circuit diagrams. It's also really well written and you can read it from start to finish.

It puts it in a historical context too which makes it fun to read.

Once you read that, they'll be fewer unknown unknowns.

[alexdowad]

This is a far better idea than "Operating Systems: Three Easy Pieces" as suggested by the OP.