Once again I need to remind potential readers that this is NOT a textbook or a reference work. It is written for the educated layman. It may have errors and omissions but these do not affect the net result. It is also not a coffee-table book, which can be picked up and browsed at leisure. Like all good works it takes effort to assimilate and repays the reader in heaps.<br><br>Some find the maths difficult. I can only say this: you will search far and wide before you find a book, which makes the mathematical foundations of the laws of nature as accessible as this. Penrose describes, explains and often illustrates all of the concepts he deals with in a singularly clear and accessible manner. His chapters on quantum mathematics and quantum physics should be published separately. They are a brilliant example of technical clarity.<br><br>Someone complained that if you don't understand calculus then you wouldn't be able to understand this book. Not quite correct! If you don't understand (a bit of) calculus then you won't be able to understand the laws of the Universe - with or without this book.