It is interesting to consider that the subject matter for this book essentially concerns only the last one hundred years or so of human history, ever since the time of Einstein's work, and that by way of comparison it only goes back to the time of Isaac Newton. Prior to Newton's day, the physical laws of the universe were understood - with the notable exception of the Greeks - almost exclusively in terms of the superstitious and allegorical. Only very recently in human history has there occurred this intense kind of scientific study, which the author describes here. Of course, the actual work involves a mathematics that is quite complicated, but the author has done a good job in telling the story in layman's terms. A few of the analogies are probably not the best in the world, but I found the book to be excellent reading, especially about how string theory developed, and only really stumbled in chapter 10, the one on quantum geometry.<br><br>While relativity and quantum mechanics are notable for being counterintuitive, string theory is especially interesting in that it fills in the gaps  (it accounts for gravity in the way the other theories do not), and provides a more intuitive basis. It makes sense to think of the most basic element of the universe as a vibrating string, certainly much more so than as a point particle. I think of a vibrating string as being a nexus between energy and the most fundamental kind of matter. It makes more sense to think that energy comes before matter rather than matter before energy.<br><br>Although the author does not directly deal with the question, it seems that he posits that string theory is an explanation of a self-contained universe. In the instances in which the fabric of space is torn, he explains that string theory provides a way for space to be mended. If the universe contracts back to the time of the big bang, it will not go back to nothing but rather to a "big crunch". Even the multiple dimensions of the theory, which lead one to think of another universe, have the sense of being on this side of the known universe. The biggest question that I could see concerns how string theory explains black holes. Is information lost in a black hole? The author seems to be on the side of those who don't think so, but concedes that there is no way to know at this point.