This is an interesting book by Madeline Ashby in many ways; in part in that the main players are not human, even though it is essentially a human world, but robots and often 'female' robot. The vN in the title is von Neumann machines, they self replicate (even if they 'male' robots), and takes a look at the dark side of having robot built with the inability to harm humans. I know Asimov got there first, but he didn't go as far as the thinking in this book, the robots are forced in many ways to be in love with humans and some of the degrading possibilities that could lead to for sentient creatures.
Also explored is what happens if the inability to harm or even to watch humans being harmed is removed do you necessarily get psychotic robots (in one case yes). The flipside of all this is also looked at from the human who prefer vNs to their own species - in places in some very creepy ways.
As a reader you are lead through some thought provoking ideas, in a fast-paced way.