It has been two years since I read this book - but it impressed me so that I recommend it highly. It is quite readable without being condescending. It uses clear text and simple but essential diagrams to explain how physics evolved from Newton's work through to Einstein's. Only very basic mathematics is used (Can you add,subtract, multiply, and divide?) so the book is approachable by any reader who has at least a vague rememberance of physics. It's the best book of its type I have read.

This is the best short book that I know of on the history of physics--equally useful for the casual observer of science and the serious physics student. Einstein is capable of presenting the basic ideas of physics in a way that is succinct yet complete--and he never loses sight of the broad, revolutionary ideas that make the history of physics so exciting. This is undoubtedly because physics actually IS exciting for Einstein, and this excitement comes through in every page.

This book reads as if Einstein thinks of physics as a really good story--complete with all characters and action of any good story--that he really wants to share with his reader.

This is an inspiring book. I know quite a bunch of people who decided to become physicists after reading it. Two interesting aspects should be mentioned. First, it was really written by Infeld, though thoroughly discussed, in a daily basis, with Einstein.(Infeld was a refugee under Einstein's protection, and thought he had to justify his temporary shelter at Princeton by writing something, which would also provide some income!). Another book by Infeld, "Quest", an autobiography, is the source of this and of many other interesting things about that period. Second, this book introduces very clearly a revolutionary contribution of Einstein's which is rarely recognized: a new method in physics which consists in obtaining knowledge from the comparison of observations of the same physical system obtained by two different observers. Though this had been done before (by Mach, for instance), it was Einstein who transformed it into a new tool for science. Physics was transformed by that, and quantum mechanics could then go even further, in the role given to the observer. This story is wonderfully told in this book.

While in high school I read a few excerpts from "Quest" in a "physics reader"; they were all about Infeld's first meetings with Einstein and Dirac. They were written very well and made a strong impression on me at the time...The book is completely different from what I expected. The excerpts I had originally seen were practically the only ones of interest to anyone interested in the major players in early quantum mechanics or relativity theory. Most of the book is about his background as a Jew in Poland, first as a child in the ghetto, then as a physicist suffering terrible discrimination, and finally how he left Poland during the war, and was saved from the concentration camps in which his family members died.
An epilog added some more history of which I was previously ignorant - why Infeld left Canada and went back to (communist) Poland.
If you have read this far you probably think I was disappointed, but nothing could be further from the truth. Infeld writes so well, and the "gossip" is so carefully analyzed, that the book makes fascinating, thought-provoking, and often touching, reading. For example, the story of how Infeld, although Jewish, was granted a "docentship" (something like an assistant lecturer) is at the same time incredible but understandable to anyone who has been involved in "politics" of this sort.
I waited 30 years to read this book, and found it to be completely different from what I expected; but I finished it in two sittings and can't recommend it highly enough.