This book provides the essence of string theory, superstring theory and M-theory.  The book starts by covering Einstein's Relativity and Quantum Field Theory and why the two conflict.  String theory purportedly connects the two although the author, in my opinion, clearly doesn't identify how it does.  Also, apparently, at least as of the writing of this book, string theory has not had a major proof that it is on the right track.  There is no confirmation proof that this is an accurate theory through experiment, etc. for a theory that has been around for about 30 years.  In contrast, Relativity was proven to be on the right track with 5 years of its publication when Eddington's observation found that light did curve around the sun.<br><br>In spite of that, this is an interesting book, from Euler's B-Formula to Calabi-Yau spaces, as a math major, I found these concepts to be intriguing.  Also, the author's description of the difference of mathematicians and physicists was enlightening.  The examples that the author provides also make this book somewhat easy to understand.  However, I only recommend this book for someone very interested in this topic.