Thanks, OT - that's helpful. That's broadly the only option I could think of bar some Apple or iCloud magic/synch function, but the tip re "ignore ownership" was something that would have stumped me!
I have 2 follow-up qs, one directly related, one not:
1) If I do as you suggest and create a new photobook on the MacBook Air (now ordered!), is there a way to copy the finished product back to my iMac so that all our photobooks are eventually in the same place?
2) After updating to Yosemite a while back, I just notcied that some of our old photobooks don't seem to have successfully transitioned to Photos from iPhoto. They first showed as a blank book icon with a cloud symbol in the bottom right corner, which I clicked expecting the photos to magically appear (about 60% of our old photobooks have popped up with images intact) but 2 days later, still nothing. The title, captions and layout are there, but no images. So my questions are:
a. is there any 'automatic' solution to get these to download to Photos properly?
b. I have (thankfully) been diligently backing up via both Time Machine and Carbon Copy Cloner. I have actually never used software to recover files/systems before, so wanted some tips on what would be the easiest way to recover the "missing" photobooks (hopefully they are in the back-ups, I upgraded several months back now), and what are the actual steps to achieve this and get the photobooks back into the Projects tab under Photos (again, so that everything is in one place).
Thanks again in advance for any help.