I have read this book at least twice now. Kip Thorne was a student of Archibald Wheeler, who I once saw give a lecture at UBC. If you were to name the top five physicists in relativity and astrophysics, both would make the list, along with Einstein and Hawking.
The book is reasonably approachable. Only basic math is involved… no tensors anywhere. It focuses on big questions, like what happens to the biggest objects in the universe (stars) when they die. For our star, the end is a white dwarf, a very dense, ever cooling dead pile of matter. For a larger star, the force of gravity is such that even the enormous counter pressures that electrons can put out are not enough to stop further collapse, resulting in a star-sized "atom" of neutrons only. For even larger stars, even tightly packed neutrons cannot stop the continued collapse and a black hole results.
Black holes are strange, to say the least. Much to strange for me to even try to describe in a few sentences. To exit a heavy star, particles have to "spiral out" in warped space. The spiral gets tighter and tighter, and the distance one has to travel longer and longer, as the mass goes up, getting ever closer to an actual circle. The event horizon of a black hole is essentially when the spiral goes circular, giving no way out of the black hole at all. Effectively, the black hole has torn itself out of our space.
And then Hawking came along a showed that black can radiate. All very strange.
The book shows how, one painful step after another, the great minds of physics have created our current picture of the universe. The good news is that it is way more interesting than the "God had a wet dream 6,000 years ago" picture that many would have us believe.
The final chapter discusses the possibilities of science fiction worm holes and such.
Lee Moller is a life-long skeptic and atheist and the author of The God Con.