Err, you've missed the point entirely.
Your implication was, in your post, that because you wouldn't buy 50 books over 2 years that no one would and thus there will be little/no market for these e-readers. Unlike songs.
The point ultim8fury and I were making is that we would easily buy more than 50 books in an e-book format. Which shows there will be at least some market.
One of the advantages of e-books is that publishers will be able to relatively easily distribute books which havn't been re-printed recently (Space Cadet for example).
Not to mention the advantages of a searchable text/reference books.
No I don't think you are looking at 'itunes' numbers. But I can see there being a good market for it.
And as for Ender's Game if it's not that good why is it that my copies keep getting borrowed by people and never given back? I mean seriously I lose at least one a year.