I really like the hardback cover on the left. The shade of red is so vibrant and attractive to me and I love how the image at the top is designed to look like a photograph inside an old-fashioned locket or pendant. Combined with the classic watch in the six o'clock position, it tells us this is a story in which time and the past are important factors.
The new international paperback edition on the right, will be released this month. And...ugh. I can see why they've gone with this cover; a blind man could see why they've gone with this cover. This is what sells in YA, right? Thin, pretty white girl. Gorgeous ballgown. Simpering expression. It's supposed to look like every other cover out there, so in that case, it's a job well done. But in trying to appeal to the US YA market, everything timeless and interesting about the original cover has been thrown out and what we're left with is something completely uninspired. Maybe this is fitting - I haven't read Ruby Red, so it may not be any different from all the other YA books flooding the market; being originally written in German wouldn't preclude it from that. But even if that were the truth, would you really want your potential readers to think so? "Buy this; it's exactly the same as everything else you've read recently!" I know that translated works are a hard sell, but I just don't think aiming to be generic is the best answer for that.
The only positive thing I can say about the new paperback is that it shows the London skyline. Setting a story in London is a big plus for me, so I'm glad the cover lets me know about it. I wish it had gone for a more interesting visual than a badly Photoshopped postcard image (it looks so cheap!), but mostly, I wish for a different cover entirely. One that takes an opportunity to challenge the status quo, instead of unimaginatively conforming to it.