title_body: Problems with ePub for iPad
upvoted_answer: For iBooks issues, your best bet is to go straight to the iBooks Asset Guide, which is available when you log in to your iTunes Connect account. As far as cover size goes, the guide says:
  
  
    The book’s cover art must use RGB color mode and should be at least
    1400 pixels along the shorter axis. For best results, a good rule of
    thumb is to use an image that is a minimum of 300 dpi.
  
  
  This applies to the cover art that is submitted along with the book, not the cover in the book itself. For the cover in the book (and for any other image in the book, for that matter):
  
  
    Images (within the EPUB) cannot exceed 3.2 million pixels. Apple
    recommends providing images that are at least 1.5 times the intended
    viewing size up to a maximum of 3.2 million pixels. You can calculate
    whether an image inside the book file exceeds 3.2 million pixels by
    multiplying the height of the image with the width.
  
  
  Assuming that you're creating an epub 3.0 file, if you add properties="cover-image" to the &lt;manifest&gt; entry for the cover image file, the cover will show up in iTunes.
  
  As far as extra blank pages go: you shouldn't need any page-break-before: always statements to break your chapters, assuming that you've followed best practices and broken the content into one xhtml file per chapter. iBooks and all other reading systems I've seen will automatically break pages for each new file.
  
  What errors specifically did you get that went away when you changed the extension of the cover image? Without seeing anything, my guess would be that there was a difference between how the file was named and what it was called in the &lt;manifest&gt;.
  
  Finally: if you're going to be doing ebook conversions, you really need to have the devices you're converting for&mdash;every reading system has strange quirks, and you're doing your clients a disservice if you don't test, particularly on devices that you know they're really interested in.