Once again I am blown away how Isaac was able to create and write this story. It feels like the story in this book is complete as the previous ones. Complete in the sense that there is no filler content, every detail of the book was used in an optimal way. All of the questions were answered and reader feels quite satisfied when finishing the book. I wonder for how long this streak for Isaac continued, well I am going to find out. 
On a side note I really enjoyed several nods to the prelude books and to the Foundation series, also done masterfully.