What are the primary distribution channels for books?

The key to retail book sales is to ensure the book is widely available through
the established wholesale and retail distribution channels. Itasca Books
maintains relationships with all of the major wholesale and retail book
distribution outlets, allowing it to place its titles in these systems. Note that
being available to the “trade” is only one part of the successful sale of a book.
The other part is creating demand through author activity and promotion.