This is worth a read, if nothing more than to see a good critque of E-books. Speaking about the PDF and HTML options:
Here, in a nutshell, is the problem with these ideas about electronic books: they treat a book as being essentially a text. A text, however, is not a book: a text is only part of a book. A book presents a reading environment which is something we’re interested in creating with Sophie. Electronic books could be much more: there’s no reason to stop with what we have.
I’ve suggested before that the problem with E-books has far less to do with display technology than that current efforts fail to understand how people read. At this point, Sophie is vaporware, but I’m encourged that the Institute for the Future of the Book understands that an E-book needs to be more than simply display of text…