Comment by radicalbyte

Algorithms in a Nutshell. Massive bang for the buck and very approachable. Get a book on Discrete Mathematics for set theory, combinatorial etc. For understanding how computers actually work, I learned to code on a 6510 so that wasn't really optional. I did check out Elements of Computing Systems: Building a Modern Computer from First Principles though which will give you a great understanding.

I didn't find SICP to be that fantastic as I already learned a lot of the principles from the masses of books I've read and software systems I've taken apart to understand.

I can also recommend taking Coursera courses on compilers, ML, architecture, anything interesting from a good US university. At least if they're still a thing :-)