If you have any interest in the history of general relativity, this book is for you. It is a gem. And in this day of exorbitantly priced books, at $36 it is a steal.

The Road to Relativity features the original manuscript of Einstein's theory of general relativity. There is something in the human psyche that is attracted to original manuscripts. Some bring millions of dollars at auctions. One thing that immediately strikes the reader is the difference between this manuscript and what is demanded by modern journals by way of preparation. Einstein's manuscript is handwritten and full of passages crossed out and things inserted. But aside from such trivialities, it is fascinating to read (an English translation is provided) how Einstein leads his readers step by step through the details of how to deal with tensors so that they will be able to follow his arguments when he gets to the physics.

The somewhat convoluted history of this particular manuscript is traced in the book's first chapter, “The Charm of a Manuscript.” Following this chapter is the annotated manuscript. The annotators are well qualified and their annotations are clear, concise, and interesting. I thoroughly enjoyed reading them. Each manuscript page appears on the left page with the annotations on the right in three different type styles to differentiate their content. We are told that the first contains material referring to the content of the facing manuscript page, the second refers to contextual background material, and the third explains a specific idea or concept. These categorizations are to be interpreted broadly; for example, we learn in an instance of the third type that in a letter Einstein wrote to his son Hans Albert, Einstein said, “I am often so engrossed in my work that I forget to eat lunch.”

The main textual material concludes with a short postscript chapter, which deals with cosmology and other matters that followed the publication of the manuscript. It even brings us into modern times by pointing out that GPS systems would not work without taking both special and general relativity into account. I remember hearing a colloquium talk many years ago by someone connected with the development of this technology. He said that the military brass (who were paying for its development) didn't believe that general relativistic corrections would matter. The speaker said they proved their point by turning those corrections off; it wasn't long before the GPS readings were wildly wrong. An interesting sideline in this chapter has to do with the frequently heard story that Einstein called his introduction of the cosmological constant the biggest mistake of his life. It seems there is no evidence that Einstein ever said or wrote this, and that it is in fact an invention of George Gamow.

There are two nice listings at the end of the book (actually not quite the end, for the English translations are at the end). The first is “A Chronology of the Genesis of General Relativity and Its Formative Years,” and the other is “Physicists, Mathematicians, and Philosophers Relevant to Einstein's Thinking.” Each entry in the latter list is accompanied by a picture and a short paragraph.

It is also worth noting that the charm of this book is greatly aided by the fanciful drawings of Laurent Taurent, which appear sporadically throughout the book.

I've asked myself what background a reader would need to understand this book. It seems to me that it can be read at more than one level. Someone who is familiar with general relativity will certainly get the most from the book. But a novice can read the annotation pages and still get a great deal of value from it. So to paraphrase what I said at the outset, if you have any interest in the history of general relativity—whoever you are and whether or not you know anything about tensors—this book is for you.

Allen I. Janis is Professor Emeritus in the Department of Physics and Astronomy and Fellow Emeritus in the Center for Philosophy of Science at the University of Pittsburgh. He does research in general relativity and the philosophy of science.