No one single book "changed me life." A lot of books, however, have impacted it. As someone in a technical field, true stories about what people can accomplish with hard work really resonate with me. A few favorites:
"The Great Bridge" by McCullough. A true story of a few hard working, intelligent men who dared to build something great and fight "the system" to some degree. It's like a real life Atlas Shrugged, if Atlas Shrugged was reasonable. If you haven't read any McCullough, you should.
"The Making of the Atomic Bomb" by Rhodes. The development of physics in the early 1900's was simply phenomenal. It's a combination of amazing levels of intelligence, men fighting against religious/ethnic persecution, and the moral battle that comes with developing a weapon.
Locke's Second Treatise on Government. Old-fashioned by today's standards, but extremely advanced when you consider the time. If you can generalize his religious arguments to more "appropriate" general moral ones, it becomes more powerful. As a big part of the basis for our country (founding fathers, etc), this seems applicable to anyone with interest in politics and government.