The printed books are zero-rated which is different from being exempt, and zero-rated supplies are taxable supplies and will count towards the registration threshold should you be required to register for VAT in the UK.
In my view, without going into detail, its your customers that should be aware that they may have to pay UK import VAT on the goods when they arrive in the UK. They may also have to pay duty too. But since these are printed books there would not be any import VAT unless the books do not meet the zero-rating criteriio as explained here: https://www.gov.uk/guidance/zero-rating-books-and-printed-matter-for-vat-notice-70110
Although the outcome of Brexit is still uncertain, Netherlands imports are mostly likely to be treated as any other non-EU import and hence you may want to read more about this here:
https://www.gov.uk/guidance/vat-overseas-businesses-using-an-online-marketplace-to-sell-goods-in-the-uk