As of right now all our orders are sourced through Ingram, so in order for a book to appear on our website it has to be available in their catalogue.
If you'd like to get your book listed on Ingram, I would recommend going to the following page: ingramspark.com. They should be able to help you out or point you in the right direction.
If your book is already available on Ingram, but isn't appearing on Bookshop.org, click here.