Albert Einstein himself explains relativity to the general public. To make himself understood, he uses everyday examples: a train running along a platform, two flashes of lightning striking at the same moment, a stone dropped from the window of a railway carriage.
You do not need advanced mathematics to follow him, from the speed of light to the curvature of space. At last you understand why time and space are not what we thought, and it is Einstein himself who explains it.
Written in a clear style, with short chapters, the book is easy to read in the language you are learning.
