I used the pageoffset to synchronize my pages with the page numbers in the book and found that the book cover then gets the number -, then goes -1, 0 and then the first page. The order is good, but it's not very nice to show -1 and 0 number of the pages. I think it would be better not to show these numbers at all, but unfortunately I can switch off the pages in the whole book, but not on two exact pages.