According to "Peopleware" by Tom DeMarco and Tim Lister, the average software developer does not own a single book on the subject of his or her work, and hasn't ever read one.
In contrast, I entered the Information Processing profession in 1977 with the attitude that all technical knowledge I possessed would be obsolete within 1-2 years. That attitude has served me well by creating an insatiable appetite for technical mastery of relevant skill sets. During my career, using my own funds, I have purchased and read literally hundreds of books pertaining to my profession, business, and the field of personal development.
Studying the masters, at whatever it is you want to learn about, can dramatically speed up the learning cycle.
These pages list various books and other resources that I recommend: