"Getting Things Done" by David Allen didn't change the way I think about everything, but it definitely changed the way that I looked at a lot of things. It's often panned today as being "common sense", but I think that's a mischaracterization - at the time it became popular, it ran counter to the conventional wisdom of how to manage your time and attention. Reading it made a profound and lasting impact on how I approached my work.
From a technology standpoint, "The Pragmatic Programmer" changed the way I looked at programming. When I read it the first time, I was a Visual Basic programmer, with only a passing familiarity with the world outside the Microsoft ecosystem. After reading that I began to explore Perl, then Python, and installed Linux and learned it. For my career as a developer, then team lead, and then manager, that book changed me more than any other book I've read in the field.
From a technology standpoint, "The Pragmatic Programmer" changed the way I looked at programming. When I read it the first time, I was a Visual Basic programmer, with only a passing familiarity with the world outside the Microsoft ecosystem. After reading that I began to explore Perl, then Python, and installed Linux and learned it. For my career as a developer, then team lead, and then manager, that book changed me more than any other book I've read in the field.