Any self-published authors who intend to sell their books direct into bookshops would do well to read this post from the Fidra blog, which tells everything you need to know about how NOT to do it.
There's also a sequel to it, in which a better strategy is revealed, which will be useful to all writers, whether they're self-published or with a mainstream, commercial house. Go and read these two pieces now. You will be glad you did. Honest.