Links to other eBooks generally are supported only by Browsers, not by eReaders.
Thereafter, within the same session, links to pages in the other eBooks should lead to the specified pages.
Ditto marks have also been removed elsewhere, as they do not generally work well in ebooks.
The Index references to footnotes have been renumbered to match the renumbering of the eBooks footnotes.
Corrected editions of our eBooks replace the old file and take over the old filename and etext number.
Some illustrations have been slightly repositioned to improve their appearance in eBooks.
No, the business and social practice of ebooks will be way, way weirder than that.