The PC, Windows, Mac or Linux can be the ereader for those that have them.
Why can't ebooks be stored in a PC or laptop and displayed on it.
The PDF format is already available. IBM has for years been distributing its manuals as book reader files on CD. Now I believe they are switching to PDF. I have several IBM mainframe libraries on sets of CDs that would if printed use up all the wall space in my house as bookshelf space.
Perhaps some people would like a more compact device but why can't it be PC based, the still to arrive tablet PC.
If publishers restrict their e-books to particular hardware format then they are shooting themselves in the feet. The fact is that no one will want to lose his e-book library when the proprietary reader breaks down, everyone will want to be able to transfer libraries from one device to another perhaps made by a different manufacturer. if someone makes e-books that will not work on my PC, I will not be buying them.