I am confused. Is the content of the individual books in Logos 5 different from the content of the same books in 4? If I want to make use of the new features in Logos 5 do I have to buy Logos 5 compatible duplicates to books I already own? That seems to be what the upgrade offers indicate. All I want is the program. I would not be interested in repurchasing my entire library because Logos has added new tags to the content of the books.