@drMerry - I did not realise all 10 times the same number were "valid" (but not really) ISBNs - as you say that sounds a sensible suggestion to check for that and discard it.
As for the multiple ISBNs, I'm going to let it be. The user wouldn't have a clue which is the right one without actually opening the book and it all just gets too hard.
I have today seen how Kovid is handling the background downloading of metadata in the new code for 0.8. I'm going to steal it and use the same approach. What it will do is use the jobs mechanism to run the extract ISBN on your books, and then pops up a dialog when it is finished toat that point start updating the books. It also looks for the last modified of the books and asks the user what to do should they have edited the book while the job was running. So that should keep people concerned with either speed or blocking Calibre happy.
That will however mean I need to rethink all those "interactive" options for choosing books. I might make it that you never get asked, and it always just uses a preferred order. Or I could make it that you can actually define your own preferred order in the configuration dialog, rather than using the preferred conversion input order. What do people think?
I will also change that scan last pages logic to look in the reverse direction for you drMerry.
My other thought which I mentioned on another thread was to add an option to allow scanning for an ASIN as well as ISBN. However is that idea flawed - do ASIN only books actually have the ASIN printed inside them? Does anyone have some examples of books with an ASIN they can give me? The search wouldn't have the same flexibility of numbers, that we changed ISBN to - I was thinking it was just search for ASIN: xxxxxxxxxx or similar. But as I say if ASIN is actually not included inside the PDF/EPUB then it is all a silly idea really