I've been publishing on Amazon and have had some moderate success (if you compare it with some of the huge sales figures that others are showing).
It's difficult to say what makes a book successful.
But Can You Drink the Water? had some reviews on Amazon.com and I was on the forums there, but I don't think the British humour was understood/appreciated by some American readers. However, when it also appeared on Amazon UK there were no reviews and I wasn't active on the boards, but sales took off. This month I've sold 10 copies in the US, but 433 in the UK. It sells for 99c/72p. When the book got into the top #100 bestseller list the sales seemed to snowball.
There doesn't seem to be a magic bullet that fits all.
