I found the cause of the problem and a fix. When I exported the book from LR4 as a JPG it numbered the images in this format aaaa n.JPG where a is alphabetic and n is numeric. I had 15 images so they where numbered from 1 to 15. The exported file was in the correct sequence. When I synced it to the iPad the order in the album was 10, 11, 12, 13,14, 15 1, 2, 3, 4, 5, 6, 7, 8, 9. When I renumber the 15 images from 10 to 25 the sync to the iPad was in the corrected sequence. So it appears that there is a sort problem with iOS on the iPad.
Andy