OK, so the book's not a reference text. Instead, it summarizes what every person should know about this wonderful universe we live in.<br><br>The book is remarkable for the number of topics it pursues and approachability of the mathematics it uses. It is not intimidating, but you'll need to make an effort to fully appreciate what the author has done. Penrose has thoughtfully prefaced his work with about 200 pages of mathematical review material that will be of little use to the specialist but of enormous help to everyone else. His writing style is both formal as well as witty, often humorous, and always enthusiastic. This is not a textbook, so there are no problems at the end of each chapter, but Penrose challenges the reader with numerous questions that appear as footnotes. This is a rather neat way to test readers as they make their way through this ponderous, but thoroughly enjoyable, book.<br><br>This book is primarily for readers who are keen on science and have some mathematical ability. But even those who find the math over their heads will benefit from Penrose's detailed narrative descriptions of quantum mechanics, general relativity, and the inner clockworks of our fantastic universe. If you don't intend to become a specialist, this book may be the only science book you'll ever need.