I loaded you “world border” shape file in QGIS. Everything works fine. But when I click with the identifying tool in one of the countries it always gives me a slightly different area derived than what is given in the attribute table: example: Area derived: 494.033,400 km2 attribute table: Area: 504782 (without unit, but I guess it is km2 as well)
where does this difference come from?
But thanks a lot for this very good book!