Yes PDF "images" can be readable, depending on the original size. If scanned from a book with pages near the size of the Cybook screen then there should be no trouble reading it. However you will not have a book, only a series of pictures of pages stuck together. It will not reflow, you won't be able to use a dictionary on the images of the words, etc. In addition, most academic books have larger pages, some even larger than 8.5 x 11. Even with young eyes, this will be difficult reading.
What I spoke of is creating editable text from scanned books. And it is true that eventually we will have equation editors, etc. but we don't now, at least in general. (There are some very specialized equation editors.)
As a comparison, I recently scanned a paperback book with over 1000 pages. Scanned at 600DPI, it took almost an hour to scan. Then I spent about 4 hours cleaning up the OCR errors. This was a good quality printed book. Cheaper quality usually generates more errors.
This experience, including one that had a half dozen equations that I kept as JPEGs in the text, is what I based my previous statements on. BTW the scanned PDF file was about 122.6 MB but the final RTF was only about 3.4 MB. IMO a significant reduction.
