or a direct quote from the HMRC, listed under zero vat groups:
Group 3 - Books, etc
Associated notice: 701/10 Zero-rating of books etc
Item No.
1. Books, booklets, brochures, pamphlets and leaflets.
2. Newspapers, journals and periodicals.
3. Children's picture books and painting books.
4. Music (printed, duplicated or manuscript).
5. Maps, charts and topographical plans.
6. Covers, cases and other articles supplied with items 1 to 5 and not separately accounted for.
Note:
Items 1 to 6 -
(a) do not include plans or drawings for industrial, architectural, engineering, commercial or similar purposes; but
(b) include the supply of the services described in paragraph 1(1) of Schedule 4 in respect of goods comprised in the items.
end of the day the cover price will be the correct price - the webstore will just be calculating the portion of the price that would be vat if vat were applicable. you're not actually being charged vat - it'll just be a glitch......