Hello,
I'm myopic too. I read my M92 (9.7) with and without glasses. For novel, it's not very important. But for the technical book, the EPUB format sometimes is not so good as the PDF version : hard to know if a part is the 'course' or an 'example'. In this case, to have a full PDF page is better mainly with I.T. books where you have some comments and some codes.
Yes, read a technical book in EPUB or PDF with a 6" e-ink device is possible, I done it with the "Managing NFS and NIS" from O'Reilly. But, know I 'm sure to prefer a 13" screen