At one level this is a piece of hard science fiction about mankind's first tentative expansion off this planet and into space. In Robert's vision of the future these steps are not taken by Governments or large corporations but by individual pioneers flying up to low earth orbit in their own makeshift way. Robert's contempt for all things government and military is a dominating, almost suffocating theme of the book but his vision is credible and well drawn none the less.
The other side of this tale is a sweeping saga tracking three generations of one of these pioneering families, the titular Gradisil being the middle generation. A common theme of revenge runs through every generation and drives most of the plot (plots) of the book.
Good but not particularly easy reading. If you are looking for space adventures then the complex emotional drama may be off putting. If you reading for emotional drama then the space stuff may not suit.