I have been using an app to catalogue my books. There are a few that are different and come up not an ISBN. Mainly James Patterson hardbacks. They have ones like 0 000000 044790
Can anyone advise.
You could search the British National Bibliography, which lists all titles published in the UK since 1950. It includes those titles published simultaneously in US and UK, but not those published exclusively outside the UK. Originally it listed SNBs, then ISBNs. Your numbers may refer to electronic books rather than to print copies.
http://bnb.bl.uk/
Or you could try the catalogue of the Bodleian Library - search for "Bodleian Solo"
They are actually books not ebooks as I am cataloguing books I own. I'm scanning barcode on back of book! I've looked inside as a few old books don't have barcodes, but no luck.