[Beerman]

I'm using iBooks on an iPad 2 and have a number of books by different authors, all in epub format (no DRM). I use Calibre to copy the books to my iPad and have noticed that almost every page in every book has some ? symbols, mostly where apostrophe's go but in other places as well.
I've tried converting to other formats but it makes no difference. Some of the free domain books have this but not nearly as much as the paid for books. I have no problem on my wife's Kindle with these same books.
What's up with this?
Thanks for any suggestions you have to get rid of these bothersome symbols.