Currently we can filter a given list by the books we already own by going to the List filter and selecting "Owned". But this will show the books we already own from the given list.

I would like to be able to filter out the books we own so that it shows only the books we don't own yet.

For example, we could do this to our "Want to Read" list in order to give someone a link to a list of books they could gift us.