take a look at a thread I created a few weeks ago:
https://www.mobileread.com/forums/sho...d.php?t=129179
I use it to read PDF files only. I don't own eBooks and won't buy any.
I use it as a PDF viewer to read scanned science books or Nature PDF articles on the way, outside in the sun, or just at home, so I don't have to hold a heavy book all the time or carry it with me.
The PDF Viewer has, compared to a viewer on a PC, a limited set of features but displays everything perfectly fine. It's fast and works.
I scan a book with the best quality possible and save the pages as image files, then optimize those with Photoshop to get a good contrast ratio, real blacks and real whites, and finally create the PDF file with Acrobat and OCR them with ClearScan. That way the file size gets reduced dramatically, the font gets converted to vectors, AND it does not destroy equations or mathematical expressions and you can search the document. So it's the best technology for science books I've seen yet. In the last step I have to crop the pages to remove not necessary margin and optimize it for the Sony Reader.
I read those scanned books in landscape mode to get a large comfortable font size. In portrait mode some books are readable pretty well, too.
But you have to optimize your books!! If you don't do it, it gets hard to read them. You can zoom in later, but only in a very limited way.
There are also some reading modes. If I want to read a Nature article stored as two or three column PDF file then I can select two or three column reading mode which works pretty well in portrait mode.
I can highlight, select and translate words in the PDF files flawlessly, add ink notes (but the pen isn't that great to write anything, rather underlining only), add page marks (ink or text).
If you have other questions, want more images of the PDF viewer, or if you want a screenshot of how a PDF book you have looks like on the Sony Reader, then just attach a page of this PDF file to your post and I'll make a few screenshots.
PS: A lot of people mention PDF reflow:
If you use science books, it just doesn't work. It does not support mathematical expressions. It works, maybe, if it's text only. But what book has text only? :-)