She hadn't actually read the whole book at that point -- but she *had* read the first book and the synopsis and some extracts for this one. :-) So when I pointed at a photo I'd seen on BevQB's blog and said "something like that would make a good cover", she said, "oooh, *yes*, that's perfect for them".

This is one of the nice things about writing for a small press that takes cover art seriously. You get more input into the cover art, and it's common for the artist to have read at least some of the book. They'll also try to keep the same artist for the series, which means later books in the series will often be illustrated by someone who's been reading the earlier books.