“Einstein was awarded the Nobel Prize for Physics in 1921, and in the same year he travelled to the United States to give four lectures that consolidated his theory of relativity and sought to explain its meaning to a new audience. A key work for anyone wishing to discover the inner-workings of one of the most important minds of the 20th century”. This book is Einstein's explanation of his theory of relativity for a general audience. The text of the first edition was translated by Edwin Plimpton Adams, the first appendix by Ernst G. Straus and the second appendix by Sonja Bargmann. The book contains four lectures, with diagrams, figures and formulas throughout. This edition includes two appendix; Appendix I on the ‘Cosmologic Problem’, added by Einstein; discussing certain advances in the theory of relativity since 1921. Appendix II Generalised Theory of Gravitation. Published by Methuen and Co Ltd, London, 1950. Publishers’ original red cloth boards, with black title and authors’ name on the spine. Book Dimensions: 19 x 13 cm and Number of Pages: 145 pages including 2 appendix, index. Condition Firm and well-bound copy. External covers are clean and in nice shape, with slight fading to spine. Internally; the book in very good condition indeed. No names or inscriptions. Pages are clean with light foxing to page edges. Inner hinges are very good, and pages are tightly held at gutters (Nice Copy) (Please see pictures).