Jackets, and covers, are a big deal to publishers. We spend hours agonizing over details that other people might not even notice; arguing over what a certain typeface 'says' about a book; whether the image is exactly right; if we should be going for an illustrative or a photographic approach; what words (beyond book title and author name) we want on the cover; whether X will put people off, or if Y will encourage a certain kind of reader to pick up the book. We cite comparative authors/books and talk about shoutlines and positioning and demographics...
We do it once, of course, for the hardback, and then all over again for the paperback. The first question we ask ourselves, in that instance, of course, is how similar to - or different from - the hardback do we want it to be?
In the case of Room, we had what we thought was an iconic hardback jacket, and so we wanted to keep some elements of that for the paperback too. For that reason, this one was quickly discounted - along with at least twenty other completely 'different' covers.