Well, to certain threshold by the seller. I think it is something like 10k. So when you go beyond that you are automatically responsible to pay VAT to buyers tax authority.

Books are already zero-rated in Ireland and a few other countries. (For a long time, _e-books_ were subject to full VAT in Ireland even though books were zero-rated, but this eventually got fixed.)

In general, sellers are obligated to use the VAT rate of the buyer's country, though there's a lot of messiness around the edges there.