Product line extensions can be made into one category (Chicken Soup for the Soul books), or into several categories: such as Weight-Watchers services, books, magazines and foods. This is a relatively low-cost, low-risk way to meet the needs of various customer segments. In addition, product line extensions:

… place a wide variety of books under a single, known brand. This can increase your exposure on limited shelf space, such as supermarkets or airport stores. 

… reinforce or rejuvenate a brand's image through repetition.

…enhance brand equity among present and new users.

… block competitive entry or raise the “price of admission.”

… can make a brand more relevant, interesting and visible.

… create a basis for differentiation.