It is much easier and far more cost effective to get your book listed in a multitude of cyber bookstores like Kobo, Amazon, Barnes & Noble and iBooks than it is to get your printed book on the shelf in bookstores.
Book publishing has changed dramatically over the past few years but the big hurdle is still distribution. A self-published author can find his/her way from manuscript all the way to printed book delivery only to find that he/she has no sales channels. Without a solid understanding of book distribution, you’ll find boxes of printed books quickly become end tables in the author’s guest room.
Most retailers and libraries, including B&N brick and mortar stores, buy books from Ingram. Retailers buy from Ingram because it allows them to buy any book from any major publisher, like Penguin Random House, Hachette or McGraw-Hill. Working with Ingram makes it possible for retailers to deal with just one book supplier, simplifying ordering, accounting, and merchandising. Book buyers very rarely buy printed book inventory directly from a self-published author.
Not long ago, retailers would not carry print on demand (POD) books but that has changed. Now, they will carry POD books but ONLY if the books are available through a wholesaler like Ingram.