This might be controversial, but I recommend picking up copies of:

- K&R

- Stroustrup's 'Tour of C++'

- Programming Practice and Principles

You don't have to do the exercises because your main goal isn't to become a programmer. But reading through these and getting an idea how data, types, memory, and files work at a low level will help add a LOT of context to using Unix-based operating systems. The first two books you can probably get through in a weekend or two, the latter is quite a bit more, but you'll go a long way with the first 8-10 chapters + the ones about I/O.

This has little to directly do with networking, but many of the resources on networking assume the knowledge that is contained in those books. Networking is a whole intimidating ocean and using high-level resources is like starting at the surface, looking down into an abyss. With these books, there's still a whole ocean to explore, but now you've got scuba gear and you're standing on the ocean floor looking up.