A good book. It has a quiet stillness and most of the book is the main character sitting around or walking in the Wisconsin countryside remembering his past and contemplating humanity, the nature of the universe and his present situation. That stuff is incredibly well done and gives the book its power. It is at its core a humanistic work.
The plot, which is the less effective part of it, involves events which literally have the power to reshape the world and the galaxy and all the intelligent beings that live in it. I found this aspect of the book quite predictable at times and much less interesting. It was the quiet reflection on the protagonists condition and the interpersonal relationships which were the most interesting aspects of the book.
There is a tendency in science fiction to focus on world shaking or in this case galaxy shaking events, and on the whole I don't think that this is the best tendency. For the most part science fiction is at its best when it focuses on ordinary people who play a small role in a larger picture or who are merely observers. Books like A Handmaid's Tale, Starship Troopers, 1984, Clockwork Orange or The Drowned World work like that and they are generally better that the ones that concentrate on people at the centre of things. This book is interesting in that it is written as if it is about an ordinary person, even though it is actually about world shaking galactic events. It gets its quality from the aspects of it that are about the small things.
The book is filled with ideas. I personally did not care for the stuff about computer generated pseudo-people who come alive. This seemed like a bad episode of Star Trek: The Next Generation to me. But the aliens are very well done.
Overall well done and worthy of its reputation.