The people i know aim at Kindle ebooks at amazon. They promote it by givining it away for free (or big discount) the first week to get reviews. And people in the facebook groups review each others books. So you can imagine the first reviews are Always good
There are more tricks to get on the front page, what is discussed in those groups. You would be surprised how the books that are the easiest to write make the most money. Like "100 ways to congratulate somebody" or more of those 1 dollar books.
'Real' writers in Holland say there is less and less to earn. I think that could be right, i see a big rise of Dutch ebooks on torrent sites.