I like to read old books and I have a Calibre library. The best books have been converted to epub, and in general, this is the best to read on my Nexus 7. I use Aldiko Premium to read. But once in a while, you come across those horrible MS 'closed quotes'. Instead of a nice double quote that's on your keyboard, they have to use the fancy typeset quotes. This buggers up the reader to no end, and you see a box with an x in it.
So, use Calibre to convert the epub to text (txt). Then use gedit, highlight the first funny box, and paste that into your replace, and replace with " (double quotes). Do the same for the closing quote. Save and bring back into Calibre (delete the original). Convert to epub, and it is beautiful! You can do the same for your hoary old txt books, since it is such a nice conversion, and easy to read on the n7.
I find I can read with the lcd screen quite well. I think the old problems were simply a matter of resolution. You can brighten or dim the screen easily. This is now my only reader. Buy one!