This book is pretty good. I’d say its the best of the three Second Foundation Trilogy books in fact. Unfortunately, you need to read the other two in order for this one to make any sense, which is a shame because the first one sucked, and the second one was ok.
A lot of loose ends get cleaned up in this book. Why did Earth get abandoned? Why did everyone forget their history? Why is Trantor built much like the cities in the Naked Sun? Why are there all those habitable worlds for the galactic empire to reside on? It seems odd that there would be 25 million habitable worlds out there. There are other examples as well, but I wont bore you with them all.
Another good bit of this book is the time line of all Asimov Foundation stories at the back of the book. I am sure it would have been useful to know about that earlier.