There are many types of booksellers, and each has its parameters of the types of books it carries because it knows what its regular customers will buy. Following is a list of the types of retailers who sell books, and some of the parameters they use to judge whether or not they will carry a particular book for sale.
Independent booksellers are typically small to medium-sized local businesses. General interest indie booksellers usually carry a decent range of titles (usually depending somewhat on store size) and focus on better-selling titles along with local bestsellers and/or a selection of books of local interest (so authors should make nice with their local indie bookseller!)
Examples of independent booksellers include Turnrow Books in Jackson, MS; Octavia Bookstore in New Orleans, LA; and City Lights Books in San Francisco, CA.
Bricks-and-Mortar Bookstore Chains
The major bricks-and-mortar bookstore chains are especially important to publishers and authors for their potential ability to buy and sell large quantities of new books and to stock backlist sellers, as well as their ability to promote books to the book-buying public through chain-wide bookstore promotions.
Most chain "superstores" carry an exceptionally large and deep selection of book titles, New York Times best-sellers and midlist, frontlist and backlist, etc.
After the demise of Borders stores in 2011, the major chains left standing are Barnes & Noble Bookseller and Books-A-Million (known in the industry as "BAM").
Online booksellers include the retail giant Amazon.com, which got its start selling books, exclusively. But online booksellers also include retailers who focus on a certain customer segment. For example, Jessica's Biscuit is an online store that specializes in cookbooks; CEO Reads focuses on business books.
Ebooks are distributed through a wide variety of digital "stores" and other distribution channels.
Subscription Book Services
Perhaps the term "book renters" is more appropriate but in 2013 a new bookselling model emerged, one that offers readers subscription-based access to large "libraries" of titles.
Non-Bookstore Retailers That Carry Books
Many types of retailers include books in their product mix, though non-bookstore accounts tend to sell a relative few titles (though they may sell each of these titles in large amounts). These accounts are typically sold by a rep in the Special Markets sales department (though that varies by book publisher). Here's some information about the non-bookstore retailers that sell books.
Special markets booksellers
These include big accounts such as Crate & Barrel, Restoration Hardware, Pottery Barn, etc. They typically carry very few titles, usually themed to go with product promotion (for example, a brunch cookbook may be displayed with waffle irons, pancake mix, etc.)
Big box stores
Book buyers for Walmart, Target, etc. are extremely selective about the product they take in, and focus on household names, best-selling books, and books that fit a certain customer segment (for example, Target might take books for its bridal registry). Midlist authors and books of niche interest aren't likely to get anywhere near these store buyers, but titles that are lucky enough to make the cut generally "sell in" to the account in very large quantities.
Like the big box stores, price clubs are extremely selective in the books they carry. Also, to offer value, price clubs (like COSTCO or Sam's Club) often ask for special packaging (like shrink-wrapping a three-book trilogy) to offer high-perceived value to its price-sensitive customer.
Gift reps and gourmet reps
Like other special markets accounts, gift and gourmet shops or store chains sell a selected subset of book products. For example, a gourmet store might focus on a handful of glossily-photographed cookbooks; a mall gift store might buy only humor books; a souvenir shop in a tourist area might focus on books of local interest; a country club pro shop may sell only golf books. Some book distributors specialize in these markets, and publishers use regionally-based commission sales reps to sell into these small, highly selective stores.
Off-price retailers such as Marshall's or Home Goods sell close-out books that have been remaindered, which allow them to charge prices much lower than suggested retail.