The book is written as a series of articles on topics such as knot topology, Riemann hypothesis and Fermat's Last Theorem. On some topics, the short article approach works just fine, on others, it seems like the topic is too big for the amount of space given to it, and the reader is left with a feeling that the subject requires a dedicated full-length work of its own. Still, the contents of the book are clear and the presentation of each topic is easy to follow.
The main issue with the book is Kindle formatting - the annotations have not been converted properly, navigation to embedded images and figures is poor, and the typesetting of mathematical characters is at time atrocious. For example, in many places, the square root symbol is omitted, completely changing the meaning of the statement. The end result is that none of the mathematical expressions in the book can be trusted by the reader.
The book could really use a new edition, with typesetting fixed, and references put in place to other popular science books that go into more detail on the topics presented within this one - the current edition prefers to present references to professional mathematical papers and books which would likely be impenetrable to its target audience.