User blog comment:Grievous67/One Piece to become the best selling book series of all time????/@comment-1940096-20150708180437/@comment-142.51.108.254-20150708224422

Isn't this a bit like coming into a discussion of which fruit sells the most and insisting that "apples and oranges aren't the same thing"?

But Unknown makes a good point. They're both part of a series, so logically the series with more books in it will sell more books. That doesn't mean it sells better.

I think a better way to compare is how many complete sets they've sold. In other words, if Deathly Hallows sold the most, and Volume 70 sold the most then compare those, rather than 78 volumes against 7 novels.

Or compare number of pages sold. However many thousands in the later HP series vs. however many volumes to make up that same count.