Not without information - can't guess what you have or did
What version of iPhoto? Did you order two copies and one was different from the other - or did you order two different books with different themes? or did you re order one book later adter upgrading iPhoto?
Unless you actually share details with us we can not help
OK sorry I didn't realise I'd not given enough info.
I have made two different books. The first one has been reprinted numerous times and always had the title printed on the spine. The second book I have had reprinted twice (on different occasions) and neither copy has the title on the spine. Both books have a one line title on the front. All books ordered through Aperture 3.4.5. When I order the second book, I'm told there is an empty text box which I cannot find, so have ordered the book all the same. I hope I have explained the situation better.
Ok 1 - you posted in the iPHoto forum but your question is on Aperture - a totally different program
2 - since you printed the book twice with identical results and you got an error message indicating an empty box I would think that is a big clue - like mayge the spine title box?
What does the preview show -
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.
3 - I will request that the thread be moved to the Aperture forum