First published in German in 1916 and issued in Robert W. Lawson’s English translation by Methuen in 1920, this short book is Einstein’s attempt to explain his own work to non-specialists. In the preface he addresses readers interested in the subject from a general scientific and philosophical point of view, assuming an education to about university entrance standard but no command of the mathematics of theoretical physics.

The book is arranged in three parts, dealing in turn with the special theory, the general theory, and the structure of the universe as a whole. Einstein builds the argument through thought experiments rather than equations, using a moving railway carriage and beams of light to show why observers in relative motion need not agree about the timing of events.

The later sections cover the equivalence principle, the curvature of space and time, and the observational evidence then available. Einstein added appendices to successive editions as the subject developed.