I'm mostly an online buyer myself. But when I go to book stores I've noticed the sorting associates the genre with the author and not with the work. This is why authors who want to write in different genres do so under pen names. So if Atwood mostly writes literary fiction, it makes sense that she would want her speculative books shelved in their usual space. This is an old mode of thinking, admittedly, but it makes sense in terms of moving physical volumes.