@quay-books Crudest approach is if your good with access or excel, the openlibrary maintains a data dump of book info in tab separated format you could use to put together a local desktop utility that you then export to CSV to then import into shopify’s product CSV import. Then when that’s working you try and move that process to something like googlesheets and connect an automator service like zapier to shopify.
https://openlibrary.org/developers/dumps
Or a paid database services like https://isbndb.com/isbn-database .
Or seeing if you can co-opt book collector software like https://www.collectorz.com or https://www.libib.com/pricing to hobble together the workflow you you need (has a kiosk mode barcode scanner thing? /shrug)
There’s also the AWS ECommerceService if your an amazon bookseller, or amazon affiliate.
Otherwise the app needs to be developed and there is actually a lot of moving parts in getting quality ISBN data.