A book that changed the way I look at life. Edwin Abbot was a man ahead (or later, depending on where you are from) of his times. In simple everyday language, he brings to the average person the concept of dimensions, something that's otherwise in the realm of mathematics and physics.
So what is great about this book?
He has painted a beautiful image of dimensions and trans-dimensionalism. He makes you imagine a world that exists in only 2 dimensions and how a person living in this world tries to imagine a 3rd dimension.
If you are a person you is trying to figure out the world, this is a must-read. Check it out sometime. Its available on Project Gutenburg.