The phrase "bookstore shelves" refers to the physical storage units in a bookstore where books are placed and displayed for customers to browse and purchase. Full definition
It's common to find the newest bestsellers showing up on bookstore shelves in hardcover, and some months later in paperback, and later still in the even more economical trade paperback. (lulu.com)
Once your book hits bookstore shelves, you've got just eight months to generate sales. (PublishingGame.com)
Worse, competition is fierce for bookstore shelf space and available media slots. (startawildfire.com)