The book contains four of Einstein's Stafford Little Lectures that were given at Princeton University in 1921. The lectures follow a series of 1915 publications by Einstein developing the theory of general relativity. During this time, there were still many controversial issues surrounding the theories and he was still defending several of his views. The lectures and the subsequent book were Einstein's last attempt to provide a comprehensive overview of his theory of relativity. It is also his only book that provides an overview of the physics and mathematics of general relativity in a comprehensive manner that was accessible to non-specialists. Einstein explained his goal in the preface of the book's German edition by stating he "wanted to summarize the principal thoughts and mathematical methods of relativity theory" and that his "principal aim was to let the fundamentals in the entire train of thought of the theory emerge clearly".