I bought a nook in the USA and I live in Ireland. I would like to buy online books from B&N but my credit card is from Ireland.
How can I add a European card to my nook?
B&N will not sell ebooks overseas (well, they did not last time I checked). I guess they may use the credit card to check that. However, You do not have to buy from them.
What matters for you is the standard used for ebooks, not who sells them. The nook uses epub, which is the main international standard (Amazon uses its own private standard). So you can buy epub books from some other source and then load them onto your nook ereader.
You can buy epub from Kobo, Humble Bundle, smashwords, Wildside Press, Baen, Phoenix Pick, and lots of other sources (my own sources are SciFi oriented).
You need to have a credit card with a U.S. billing address to make purchases. So, I am afraid, you won't be able to add a European card.
