"Networking for Systems Administrators" by Michael W. Lucas.
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.
Wanted to bump this. It's the book I recommend when someone asks, "How can I learn networking".
My next favorite is the Top-Down book everyone above mentions. I like that it starts with loading a web page, instead of bits on a wire. And they have pcap files so you don't even need a lab.
The Stevens book is the standard text for programmers writing network code.
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.