Hello and thanks very much for your reply. Here's a few answers to your questions:
System: OS X 10.6.8
Iphoto: 9.2.3
I've tried Preview - It shows pages 1 and 2 to be what appears to be the front and back covers (incl flaps) plus checking each photo.
Also tried uploading an old book that I had previously bought successfully. It also increased page number by two and failed to upload.
Library: In 'Pictures'
Checked for updates, in frustration, but says "none available"
Not sure what managed v referenced library is.
Mac: 21.5 inch Mid 2010
Free space on boot drive: 156.81 Gb Total space 500 Gb
Theme: 'Picture book'
Pages: 98 (payment page accepts 98 and prices accordingly, but on assembly it says there are 100 pages)
Assembly happens ok, but upload doesn't.
Summary: I'm wondering if the problem is not having updated system or iPhoto, and whether the additional two pages is merely a symptom of that. But, have been reluctant to seek upgrades as everything has worked beautifully until about March/ April this year. Since then I've now had problems with four books. Everything else works fine.
Not sure if the above is of any help to you but would be grateful for any advice.
Helenafromgarran