The story is entertaining & has many didactic features. Pickover also inserts some humor so as to make the book enjoyable as opposed to a dense treatise of rather complex mathematical concepts. Also, at the end of each chapter is a section called "The science behind the science fiction." It is a detailed account of what we presently know (or think we know) about the notions which were presented in the narrative.
And, the concepts are many. We learn of various weird things that happen in & near a black hole, such as time slowing, the "shrinking" of one's perspective due to the singularity & the mind-numbing gravitational power which is projected by black holes.....a gravity field so immense that the escape velocity exceeds light speed. We learn how black holes were predicted by Einstein's theory of Relativity as well as how the many principles of quantum mechanics come into the picture when one is attempting to understand the nature of singularities.
Much of this book is speculation, but it is educated speculation. The conjectures on what happens inside of a singularity, as well as the possiblity of wormholes which lead to other universes & dimensions is exciting & based on our best available current knowledge of the cosmos. As an added bonus, there is a chapter in the back of the book in which many of the world's leading cosmologists answer questions posed by the author on various topics about & related to black holes. There are also computer animation pictures of some of the more dazzling geometrical effects that are generated by black holes. For anyone who is planning to visit a black hole anytime soon, this book is a must.
Overall it is an excellent overview of Black Holes, and a joy to read!