If the problem persists and if you are sure yoru internet connection is good then
Before ordering your book preview it using this method - http://support.apple.com/kb/HT1040 - and save the resulting PDF for reference - the delivered book will match it.
and boot into safe mode and try
If you can't create a PDF file of the book boot into Safe Mode, Mac OS X: Starting up in Safe Mode, and try creating the PDF file there. If that's successful preview the PDF file for any errors and then order the book from the Safe Mode.