The Ouroboros Wave is a textbook example of diamond-hard science fiction: in this somewhat philosophical space opera, one suspects author Hayashi didn't simply look up gravitational strengths and orbital periods, but calculated them himself. As in all good hard sci-fi, the technical details are an integral part of the setting and plot, and as in all good hard sci-fi, those details are right.
This book is not a novel, but a collection of six linked stories, spanning much of the 22nd century, and a good portion of our Solar System as well. In Hayashi's future history, humanity discovers a small black hole in the outer reaches of our Solar System, whose unstable orbit would put it on an eventual collision course with our sun, though not for centuries at the very least. The most far-seeing of our race pushed forward an ambitious program, not merely to prevent “Kali,” as the black hole was dubbed, from making contact with the sun, but to actually capture and use it as an energy source. Thus the Artificial Accretion Disc Development association (or AADD) was born.
There are two common themes to these six stories: the nature of intelligence (and possibility of non-human intelligence); the socio-political changes (and conflicts) that occur when the most adventurous and, arguably, most intelligent of our species leave the home planet for a massive scientific enterprise, and the rest . . . don't.
The science is epic. We get to check in on a multi-generational project at various times throughout the century. Early on, as the black hole is still moving towards its stable orbit around Uranus, later on, as the initial, thread-like rings are being expanded into a true Dyson sphere. We also get a sense of the changes wrought throughout the Solar System as a direct result of the energy provided by, and organization built up around this project. This includes the increased strain between the Earth government and the society that has developed away from it.
Hayashi is fascinated by the idea of leaving this planet behind and taking our next step as a species: terraforming Mars, exploring Jupiter's moons, sending the first manned probes to another star system. He imagines Kali as the economic and political push to finally make this happen. His stories also suggest that the accelerated scientific progress resulting from AADD is just the thing to start making our next big discoveries about the universe, like whether or not we're alone in it.