I found this book to be mildly entertaining, with few OK puns that were greatly diluted by the mediocre ones. This sci-fi is pretty low on "sci" and not too high on original "fi". The most annoying recurring phrase was "he was right...". It repeated too many times throughout the book and tasted like yet another spoonful of sugar in the same cup of tea. I was somewhat bored. However overall, it is not the most horrible piece of literature I was exposed to.
This was my first Spider Robinson book and maybe I should have read the previous Callahan's books first to better understand the story. I thought it was plain stupid. Looking at the reviews - you either love it or hate it. I did not want to waste a credit so I listened to the end - would not recommend this book to anybody.