Collections

I've read the Collections section, but maybe I'm missing something. I want to "join" 2 collections. Is there an easy way to do that?

I have a total of 595 books in All Collections. I have 197 books in Your Library. I have 398 books in My Books.

I want Your Library to be in My Books, so that My Books has 595, the same as All Collections. How do I make that happen?

What you want is Power Edit. You activate it by clicking on the lightning icon in Your Books. After that it should be obvious how to proceed. Don't forget to click on the icon again when you are done to turn it off again.