Book distributors are companies that promote and sell books to retailers and libraries, typically through sales reps and/or printed catalogs. Distributors usually purchase books at a steep discount (65% to 70%), warehouse the books, and ship them to book wholesalers, libraries, bookstores and other retailers.
Distributors handle books that are published independently (not through a “self-publishing company”) and have strong sales potential. Members of the Independent Book Publishers Association (IBPA) are eligible for special deals with Partners Publishers Group and Small Press United.
Book wholesalers process orders and ship books. Being listed with a major wholesaler will make it easy for bookstores (including Amazon) and libraries to buy your books, but you are responsible for generating demand. Ingram and Baker & Taylor are the largest and most important book wholesalers in the U.S. They typically buy books at a 55% discount and they offer paid advertising opportunities to publishers.
If you publish through a subsidy publisher or “self-publishing company” your publisher will probably get your books listed with Ingram and/or Baker & Taylor.
If you publish through CreateSpace, sign up for the “expanded distribution” program to get your book listed with Ingram and/or Baker & Taylor. (You have to use a CreateSpace ISBN to get into Baker & Taylor). Details are here. You can learn how much money you will earn through various sales channels here.
Another way to get your book listed in the Ingram database is to print it through Lightning Source, which is the largest print-on-demand printer in the U.S. and is owned by Ingram. See this article for details about using Lightning Source and determining your wholesale discount.
If you published independently and don’t have a way to get listed with a wholesaler, you can pay to get into Ingram and Baker & Taylor through the programs offered by IBPA, but you’ll need to determine if the fees are worth the potential benefit.