I've talked about elements of book design before, like here where an artists talked about
creating cover art, but what about the process from the publishers point of view. Below is a great little video on the process of making a book cover.
What I thought was interesting was that when the publisher is talking about the collaborative process behind cover design, the author is listed last, almost as an afterthought This, unfortunately for the author, is very much the way things work.
I fill out a cover sheet at the beginning of the process (basic info like descriptions of hero/heroine, and a make a note of a few important elements of the story), that's basically it until the cover is complete. Only very famous authors get more say on their covers. The feeling within publishing is that authors know how to write, but publishers are the experts at marketing that book (sometime this is true and sometimes it's not).
I think a quote from
Ilona Andrew is apt (unfortunately I can't find it, so I'll paraphrase). Basically someone was complaining that they didn't think the girl on the cover looked like they thought she should. Ms Andrews said that when readers see certain things on covers it gives them cues as to what sort of book it's going to be (romance/ fantasy/ thriller). The publishers understand those cue consciously authors may not. Of course that's not to say publishers always get it right.
The other thing to bare in mind is that authors can moan like drains about their covers, but they are going to have to have a very, very good reason, because changing covers costs money.
Click the image & enjoy the video: