I'm not sure about this either as I've heard various explanations. One explanation says that the book publisher can hardcode in the page break tags to make the pagination of the eBook close to that of the printed version. However, if the publisher does not hardcode the page break tags then ADE uses the 1 page = 1024 bytes algorythm. Perhaps someone can enlighten us with certainty (not speculation) on this matter.

This much I know for certain: Pagination of the same books on my 300 and 900 are the same. If I read to page 221 in a book on my 300 and then switch to the 900 to read the same book, I can use the Goto page 221 function and quickly find the location.