After completing the final version of his general theory of relativity in November 1915, Albert Einstein wrote a book about relativity for a popular audience. This new edition of Einstein's book features an authoritative English translation of the text along with an introduction and a reading companion that examines the evolution of Einstein's thinking and casts his ideas in a broader present-day context. A special chapter explores the history of and the stories behind the early foreign-language editions in light of the reception of relativity in different countries. This edition also includes a survey of the introductions from these editions, covers from selected early editions, a letter from Walther Rathenau to Einstein discussing the book, and a revealing sample from Einstein's handwritten manuscript.--