Are there mistakes in the quotation

To explain in what has consisted the revenue of the great body of the people, or what has been the nature of those funds, which, in different ages and nations, have supplied their annual consumption, is the object of these four first books.

I read the above sentence from The Wealth of Nations on my kindle, but I wonder if there are two mistakes? The first is "To explain in what..." , the second " these four first books ".
I feel that the first should say "To explain what has consisted of..." , the second " these first four books ".