I've seen a couple of these floating around so I thought it'd be fun to examine each of the alternate covers of 172 Hours on the Moon.
This is the final American cover, and I really like this one. It's simple but striking, with the combination of the creepy eye and dusty moon landscape. The black background is perfect, along with the not-overdone text.
The UK cover has nice text and a neat tag, but I don't like much else about it. The girl just looks depressed, and the image along seems a lot more like something you'd see in a contemporary rather than horror/sci-fi-ish novel.
Here are two alternate covers that were ultimately not chosen. I like the landscape with earth on the left but the rest looks too-homemade. The one on the right is very cool, and I especially love the contrast between the "172" and the prints, but it comes across as more science-fiction and less horror.
Two more alternates! The left is simple and neat, and the more I look at it, the more I like it. The only downside is that it's just not as creepy as it could be. The one on the right is a neat concept, especially after you've finished the book, but it's not as elegantly creepy as the original final, if that makes sense.
All in all, my favorite is the first cover. What's yours?