Hi
I’m sorry, but you say you have a Cybook - is this true or are you just thinking in getting one?
If you have it, haven’t you tested it with Pdf already?
If not and if you want an example with the Cybook check this post:
https://www.mobileread.com/forums/showthread.php?t=30562
It gives an idea of what to expect.
To recommend: would recommend the Iliad, and if not the Cybook but with the Pdf reflow text of the Sony as an option (besides it’s own zoom), so one could choose what way he/she would like to use… of course this second option does not exist today…
Best regards,