We can look for books by either keywords (of the title, the authors,etc) or by isbn/ean. We look for books on internet sources. Note that… we don't have a source for english books yet, just tell us you're interested.
We can scan the barcode and find the book information with an usb barcode scanner, it works and there is no setup needed.
If you already have ISBNs alongside their quantities in an Excel or LibreOffice calc sheet, we can import them. You need to export it to a csv file first, and then refer to this documentation.