One of the best histories of anything physically important that I have ever read. I ordered it in paperback to use it but I've now got a hardback copy as well. I did the same thing with the Feynman lectures. I mess up the paperback copies as I work with them and have the hardback copies for reference. A really great companion to these is Fundamentals of Physics (I bought the 8th extended edition) Jearl Walker (Halliday, Resnick and Walker). Dr. Walker now edits the book, I think. Penrose's The Road to Reality is well written and topics normally far from the understanding of most of us are well stated. Two years ago, this book alone started me on a journey that was only begun in 1965. The other books are essential to get at the rigor of solving problems. But Penrose tells you why it is important and how to approach the process of thinking.