Started on the book, and it's sometimes still used as a reference. Since getting dual monitors, I'd been using the web almost exclusively.
The way I learned how headers (and linking) worked was trying to get an OpenGL application to compile and run. Even though it wasn't my own code, I did learn a good bit just by doing something random (included some minor debugging as well), and I was successful after a couple nights. So, I learn by looking through samples of what I'm interested in, hand copy it down several times over while studying how each piece works, and modify and eventually, apply it to my own ends.