I was interested in aviation well before starting ATC training, and I think the learning/knowledge that made one of the larger differences was meteorology.
I'd recommend reading any books to do with aviation weather. Those aimed at glider pilots are among the more readable, but once you start to understand it, it becomes fascinating.
Or not. There are those that find met interesting, and those that don't. Either way, it's useful.
Our workplace is the sky. Good to know what goes on.
Any text book to do with flying, in order to increase knowledge of aircraft, is good. Fiction, too, if written by those that know.
Try Stick and Rudder, and Fate is the Hunter for starters.