@gregroyj42: This is definitely not suitable for a 6 year old.
A character goes to a planet called Sextillion, where an orgy is depicted with genitalia displayed. There is child prostitution, child birth, frequent swearing, graphic blood and guts, violence and robot headed sex in the first volume alone.
No doubt though that this is a great story for mature readers.
@ComradeCold: I am collecting the oversized deluxe hardcover editions at the moment, they are really nice on a book shelf and have a quality feel to them that does the series justice. I currently have the first three volumes out of the five it's collected in, will get the other two soon when I have some spare cash, can't wait!