Relativity: The Special and the General Theory is Albert Einstein's own accessible introduction to his revolutionary theories of special relativity and general relativity.

Unlike a modern university textbook, Einstein wrote the book specifically to explain the fundamental ideas of relativity to readers who had a basic understanding of mathematics and physics but were not necessarily professional physicists.

The book explores one of the biggest changes in our understanding of the universe:

Space and time are not absolute—they depend on the state of motion and the gravitational environment of the observer.

Einstein develops this idea progressively, beginning with familiar concepts such as space, time, motion and geometry, before moving into special and general relativity.