Although this is a very illuminating book (I gave it a 4-star rating), contrary to its claim in the preface, this is NOT for those whose math background is limited to a high school level. You need a firm grasp of advanced calculus, abstract modern algebra and topology to follow the brilliant logic of Roger Penrose in this enormous, encompassing work. If you do have this minimal background in math, this book will delight you. However there is one small criticism and that is on page 960 where Penrose dismisses Category Theory as 'abstract nonsense'. What seemed to have escaped the brilliant man is that Category Theory has become the 'language' of K-Theory, which the latter has become instrumental in the study of D-branes in String Theory. That Penrose fails to mention the very existence of K-theory in this book makes its sub-title, `A complete guide to the laws of the universe', incomplete.