The book that has changed my life the most, so far, has been The Structure and Interpretation of Computer Programs by Abelson and Sussman.
In 2010 I started a job that was far, far ahead of my skillset. I'd written fewer than 10,000 lines of code in my life, and I was completely ill-prepared for the work I was supposed to be doing. I picked up SICP about a month or two into that job.
Fast forward a year, and I felt that I knew more about programming than half the people I worked with, and I'd moved to a smaller, more awesome company doing work that I think is much more fun.
A year since then and I've picked up half a dozen new languages, given talks at user groups on some of them. Next year I'm aiming for conferences.