This is definitely the most comprehensive book ever published on theoretical physics, written by one of the most influential theoretical physicists alive! But the reader should be forewarned : it is not easy reading, even if one skips the maths, as Penrose suggests in the Introduction...<br>Now, if one wants to understand everything, then it becomes really challenging, and I don't think many readers would be up to it. By understanding everything, I mean understanding enough to be able to do the exercises, and , believe me, this is no easy task! Especially that the author forgets most of the time that this is supposed to be a book for the "general public",so he writes as if he were giving a lecture to his graduate students.That is, he assumes that the reader knows already a lot about the subject at hand. Take, for instance, his explanation about the "clock paradox" of Special Relativity : not only is this explanation very special to Penrose, but he does not even explain what the "paradox" is all about! And so the reader who encounters it for the first time would tend to think that the paradox is only the fact that the voyager ages slower than the observer who stays behind, which is not altogether true...There are other examples showing Penrose not at his very best: the presentation of the Davisson-Germer experiment,at Chapter 21, leaves much to be desired, as it does not explain its true predictive property, that of interference fringes. And there is one place where Penrose talks utter nonsense: it is at pages 77, 78 and 79, on the issue of the sum of the series of general term x^2n. Penrose seems to believe, and this is astonishing, that this series is the development of f(x)= 1/(1-x^2) for all values of x. In fact, this is only true when the absolute value of x is strictly &lt; 1. In all other cases, the series diverges and has nothing to do with f(x)! The proof of what I am saying can be found in any elementary calculus textbook. So, with x= 2, we are bound to get a perfectly absurd value such as -1/3, because we are using a wrong expression for this series!Penrose goes on and on , pretending that Euler used to  "hold to such absurdities", which I don't believe at all,  and ending up by saying at page 79 that " it is perfectly possible to give a mathematical sense to the answer "-1/3" to the above infinite series", comparing this case to the "logical absurdity" of finding real solutions to the equation x^2 + 1= 0...I don't see the relevance of this equation to the subject at hand! Indeed, this equation has no real solutions, and it was only solved by the introduction of a new class of numbers, the complex numbers. But the infinite series of general term x^2n will always diverge to infinity when x &gt;= 1, and there is no way it can be made equal to -1/3 for x = 2, since we are only adding positive powers of 2 here! I honestly don't know what to make of all this nonsense, coming from a mathematician of the stature of Roger Penrose! I also wish these three pages could be removed from this book...Now, if Penrose can make such a blunder with an elementary subject like this one, who knows if he is really making sense for much more complex issues?This is why I have added "to be read with care" to my original title, and I have removed one star from the rating, when I went over my review on 4 April 2010...<br>The other aspect of the book that struck me is that Penrose distances himself from mainstream physics on two very important paradigms: spontaneous symmetry breaking in the early Universe, and inflationary cosmology. For him, there is no sufficient observational evidence for these two "speculative theories", as he calls them. Many cosmologists and physicists would surely disagree with him, but he has the honesty to express his beliefs, even when they are "out of phase" with those of other "pundits".And he has some very solid arguments, stemming from a deep insight into the Second Principle of Thermodynamics. It would be very interesting to see what the "inflationists" have to say about Penrose's arguments!<br>Another very significant fact is that Penrose does not show any sympathy whatsoever for Superstring Theory, preferring his own "twistor" approach to QFT. In this,  he joins other theoretical physicists, such as the Nobel laureate Sheldon Glashow, and lesser figures like Lee Smolin(see his book The Trouble with Physics) and Peter Woit(Not Even Wrong), who have been complaining about the non-falsifiability of SST for quite some time...Let's hope that the Large Hadron Collider at CERN will be able to settle this issue, one way or the other, in the near future.<br>But be that as it may, I would not hesitate to recommend this book to all  those readers who, like myself, are passionately looking for an explanation to the laws that govern "Reality", i.e the Universe we live in.<br><br>Finally, I would like to add here that "Publishers Weekly" makes a comparison between this book and Hawking's "A Brief History of Time". But this comparison is untenable: Hawking's small book is but child's play compared to this treatise!