
Incidentally, if you suspect you yourself are this, I can't recommend any book more highly than Michael W. Lucas's Networking for Systems Administrators. Don't be fooled by the title - the whole idea is to get you to the level where you can talk to a network engineer without looking totally clueless, and no farther - an excellent stopping point.
I would recommend it handily over, say, my own Intro to Networking class in college. And yes, `mtr` is mentioned by name in it!
- Networking for Systems Administrators, by Michael W. Lucas. Its explicit goal is to teach you just enough about networking, from the electron up, that you can talk to an actual network engineer and not make a fool out of yourself. It's a phenomenally high-ROI read if networking isn't your strong suit.
- The first 3 chapters of Mastering Regular Expressions. Regexes are up there with Vim keybindings in terms of sheer ubiquitous use no matter what stack you find yourself in. The rest of the book is excellent if you want to actually implement a regex engine.
- The Art of Unix Programming. Less technical. Gives you an idea of why exactly 'nix machines are like that, especially older commands. The 18 rules of design are worth committing to memory.
- The Linux Programming Interface. More technical. Pairs esp nicely with the above. Lots of practice C code one can run, plenty of short self-contained chapters.
- Not a book, but an online paper: https://how.complexsystems.fail . I see echoes of this everywhere I work, and it often helps me understand what kinds of "bad" things are secretly highly evolved resiliency measures.
- The Little Schemer. Just for the joy of solving problems.
Most of the others I can think of are too specialized to be of worth to everyone, but for what it's worth, William S. Vincent's Django for Beginners, APIs, and Professionals are a lovely triptych for anyone wanting to get into backend web dev.
In retrospect, should've been called "Networking for programmers". Short. Concise. Examples for all operating systems including Windows. That will get you started. After that, to level-up, any book with good ratings would do. And you will also know which part of the networking stack you want to learn more about, thus, you'd pick the correct book for yourself. But this one is a must have if you're feeling very uncertain about your understanding of networking concepts and how everything glues together.