I can't buy a book to the apple store. Why?
IT is second time to have the same problem. Please check in yours servers what it is and fix this bug forever.
iPad Air, iOS 9
You are not addressing Apple here. This is a user to user support forum. Since you do not indicate any error that you receive, your best selection is to contact iTunes support with your question. http://www.apple.com/emea/support/itunes/contact.html