This is an impressive work that explains the highly complex non-intuituve string theory in amazingly lucid clear writing style to the general public. Similar to many physics books  which survey classical theories for the readers, Greene offers his own elucidation on relative motion in special relativity and in  warped space in general relatvity that is even more detailed and clear than some physics text books. His transition of how String theory offers a solution to bridge general relatvity and quantum mechanics because of String theory's geometry to cope with quantum undulation at the microscopic scale is very intuitive and helpful. His explanations on how the 3 families of particles in Standard Theory are best explained by just variations of vibrating strings frequency and strength are also relatable and convincing.Greene's use of the garden hose universe to explain the curled up dimensions in string theory and how they are  hidden from and connected to extended dimensions is exceptionally lucid and helpful, making us easy to grasp how 3 extended space dimensions we experience are related to 6 curled up space dimensions, together with time making up 10 dimensions. The 9 dimensions don't just crumbled up in any shape but in a unique 6 dimensional Calabi-Yau shape derived from many researchers calculations. Hence, the universe is made up of the Calabi-Yau shape manifold in curled up 9 dimensional space configuration together with time. The final 11th dimension space is explained by the need of the two dimensional membranes in M theory which is used to resolve the dilemma of 5 version of string theory. Greene further explained that the five versions are just different depiction of string theory with three of which Type 1, Herotic O, and Herotic E being large/small radius duality equivalence of each other and with the rest of the two, Type IIA and Type IIB, having the same reciprocal dualiy. This whole 11 dimensional geometric scheme development is carefully and lucidly written with unmatched clarity over these connected concepts of Kaluza-Klein theory, Calabi-Yau, shapes and M theory.Though Greene does not use the actual equations from perturbation approach and Kaluza-Klein geometry of String theory to flesh out his explanations, it is still not easy to conceptually grasp the concepts of String Theory for anyone who does not have university level education in physics or mathematics. Greene actually warns his readers about the difficulty of the subject despite his best effort. It takes work to get through this work.Another feature I like in any physics books is the anecdote stories of the journey of the physicists doing research. Greene shared his stories of his journey in String theory. The separate research efforts on the mirror symmetry Calabi-Yau shapes for space tearing flop between Greene's group, to include Aspinfall and Morrison, while at Princeton, and Witten is an interesting story. Greene also included various stories of String theory second revolution in 1995.Overall, this book is a brilliantly clear introduction to string theory that is going to be a classic.