The USA cover is beautiful, but the UK...honestly, I think it is not very appealing. Has the author of a book any influence on the cover?
I have to admit, I judge books mostly by their covers, so, should I ever write a book I could not accept an ugly cover.
Some of the "Chronicles of Narnia" covers are really pretty:
http://www.amazon.de/dp/3800050048/
Ah to have a say in the matter. Would you rather not be published or have an ugly cover?
The thing about my UK cover is this. It was wrong. It isn't ugly, but it is marketed to the absolutely wrong age group, far too young. Interestingly though, I have had people tell me they much prefer the UK cover to the USA one, so don't forget it is all a matter of taste.
But really, the author is the last person to have a say on their cover. Aside from the editor and marketing department, there is also one other group that I never thought of before I was published, and that is the book buyers. If the buyer for Barnes and Noble says, "Well the books sounds interesting but you have to change the cover or we won't buy any" by gum the publisher changes the cover. Because Barnes and Noble is responsible for selling a heck of a lot of books.
There is so much more to it than just our opinion.
Nonetheless Scholastic UK were wrong with my cover. They have acknowledged that, and when the book comes out in paper back in May, it will have the North American one.
I am lucky. Very very lucky. I have a publisher who was willing to admit they made a mistake and fix it. Not every author is that lucky, and unfortunately it is our lot to have to deal with it.
I have learned, when it comes to both title and cover, you can hope for the best . . . but there is only so much you can do if it's the worst. An agent is helpful in that, but even they can't work magic.
So I guess it is up to you. Do you really want not to be published, with a cover that may actually be marketable but you just can't see how, or not published at all . . .