This might just be the best of the series, if you ask me, though I didn't read the sixth yet. Some interesting, but horrifying, concepts are presented here. One has to wonder if that's what it'd take to make humans at least appear to get along with each other. Probably so.
And it also shows the full extent of the timespan of the series. Amazing vision from the author, but I still hate it for the "reality" of everything in it.