Book marketing is relatively simple (but not necessarily easy) because there are only two arenas in which to compete: retail and non-retail. The retail sector consists of bookstores (bricks and clicks) and other outlets such as office supply stores, supermarkets, airport stores, warehouse clubs, health-food stores, gift shops and specialty stores.
Selling to these establishments is primarily done through middlemen that control the flow of goods and who exact a fee for their services. Sales through these channels are plagued by two other factors that deteriorate profits: returns of unsold books and payments in 120 days or more.
Publishers may also sell to libraries, and then consider their sales opportunities exhausted. But there is a significant source of profitable revenue in the non-retail arena. This is made up of buyers in corporations, associations, schools, the military and government agencies.