Book rights, and especially eBook rights, can be messy. UK publishers can’t just start selling books in the US, and vice versa. For most modern books by big authors, you’ll see the hardback and eBook versions being published at pretty much the same time around the world. For older books that were released before eBooks were a big deal, and for smaller authors with publishing deals, however, you’ll regularly find that the eBook version is available in some countries and not others.