The reviewer of April 13 from Moscow, Idaho says this is not the book to read unless you already understand the theory. Maybe fair enough. It was written when Einstein had achieved youthful fame, though, not in his dotage, if he had such a thing. It may be a little more difficult for the translation, but not much. Contrary to some reviewers, it is not that easy to follow, and if it seems like an easy read, you probably haven't understood it. There are many books written since where it is probably easier to learn about special relativity, to say nothing of the basic ideas of general relativity. But once you have started to get the hang of things, this book is a masterpiece of exposition! It allows one to follow Einstein's actual thought process in arriving at these theories -- pretty much by a process of pure thought -- more or less in the steps he probably took himself. There is not a word in the exposition that was not carefully thought out. So, learn the theory somewhere else and then read this book -- you'll understand the theory better for reading Einstein's book -- or read this book first, keep going back to it 'til it starts to make sense, and maybe consult some other, more "user-friendly" textbook at the same time. Einstein claims his book allows a lay reader with only high school math to understand relativity. To which a friend of mine replied "Yeah, if you have an IQ of 800". To which I say, have patience, keep thinking about it and going back to it.