As far as I can make out, the first one (mostly white, whale at the top) is the Canadian edition. The one in the middle with the curtain is the American edition (even though it's what I have from my Canadian library). And the third (blue and yellow) is the UK and Australian version.
I'd love to know the reasons behind the decisions of publishers' marketing and art departments for their different cover designs.
In this case, I prefer the first one (the Canadian edition).