Arthur Stanley Eddington is one of the most influential astrophysicists of the 20th century. Born in Great Britain, he is credited as being a leading teacher of Einstein's theory of relativity in the English world. He is considered a great philosopher of science, and was a boisterous advocate for the popularization of science until his death in 1944. This book, Space, Theory, also titled Space, Time, and Gravitation: An Outline of the General Relativity Theory is one of his most important and well-read books.
Originally published in 1920, this book was written at a time when information from Germany would have been limited, and thus many of Einstein's theories had not yet been completely digested by the Western world. The purpose of Space, Theory is to present the theory of relativity to those without a strong scientific or mathematical background. While mathematical equations do make frequent appearances throughout the text, they are complemented by detailed textual explanations and real-world examples.
The book is presented in a logical manner. The first chapter discusses the very nature of geometry, and how Euclidean geometry is not sufficient for a discussion of the theory of relativity. One must always consider the dimension of time, Eddington argues. It is this discussion that sets the stage for the remainder of the theories presented in this book.
Almost one hundred years after it was written, there are still few better books introducing Einstein's theory of relativity to the layman. Eddington is gifted in taking immensely complex theories and breaking them down to a level that demonstrates their significance in every day life. If you are at all interested in astrophysics, Space, Theory is a must read.