This final book of the master was a joy to read. Here, he returns, one last time, to many of the favorite topics, characters, and settings of so many of his other books and stories. All in one book you have time travel, alternate dimensions, robots, a vast brotherhood of friendly aliens, a very dog-like wolf (ala City), not to mention many other familiar elements. It is all contained in a very complex, skillfully woven, unpredictable narrative.
It is fitting that that this book should address the issues of immortality, eternity, and the purpose of life. After all, it was written only two years before the author died (peacefully and in his sleep.) You find immortality achieved by means of fields that hold time at bay, by artificially becoming points of pure intellect, by evolutionary means, by intelligent machines, etc. There is also the understanding that mankind has infinite potential to grow in intellect and understanding. Indeed, it is clearly stated that without consciousness and understanding the universe would lack meaning. That is the ultimate purpose of all sentient beings- to give meaning to the universe.
This is a mature, thoughtful, science fiction novel. It is not an old style shoot-em-up space opera, though it does have some pretty good killer monsters in the pay of sinister aliens from the future.
All in all, I found this novel to be an excellent capstone to a distinguished career. The old magic never dimmed. I actually postponed reading this book, for I knew that there would be no more coming after I had finished this one....