I have had the same problem. After two fruitless hours on the phone to Apple "Support", no progress, and no promised email later either, so I downloaded Yosemite as my operating system. A slow process, but it worked. Then panic: my carefully prepared 72 page book wasn't there. Eventually I used Finder to find the iPhoto Library (in Yosemite it's just called Photos) and was then asked if I wanted to switch libraries. This I did - and lo and behold, I got the book back and, what's more, I have successfully loaded it and received confirmnation that the order is on its way. So, you could try this.
LizHR