Relativity: The Special and General Theory (en Inglés) - Albert Einstein

Relativity: The Special and the General Theory began as a short paper and was eventually published as a book written by Albert Einstein with the aim of giving:

...an exact insight into the theory of relativity to those readers who, from a general scientific and philosophical point of view, are interested in the theory, but who are not conversant with the mathematical apparatus of theoretical physics.

- from the Preface.

It was first published in German in 1916 and later translated into English in 1920. It is divided into 3 parts, the first dealing with special relativity, the second dealing eith general relativity and the third dealing with considerations on the universe as a whole.There have been many versions published since the original in 1916, the latest in December, 2011. The work has been labeled as unique in that ir gives readers an insight into thought processes of one of the greatest minds of the 20th century.