If you want to go to the extreme: delete first copy.

You can; as I understand it, the only legal requirement is that you only use one copy at a time.

ie. I can give my book to a friend after I’m done reading it; I can make a copy of a book and keep them at home and at the office and switch off between reading them; I’m not allowed to make a copy of the book hand one to a friend and then both of us read it at the same time.