I love secondhand bookstores. Next to libraries, they are the best place to get the greatest book value for the dollar. I discovered the joys of secondhand bookstores when I attended graduate school. It was a way for me to acquire books I enjoyed (I filled out much of my Isaac Asimov collection from such places) without breaking the budget. I did not have much money to spend on frivolous items so spending just a few dollars for a book I would read more than once was a great deal. I also had a library card but if I really liked a book or an author, I would acquire my own copy.
Not only can you buy books from a secondhand store but they also purchase your books from you. My favorite secondhand bookstore gives its customers cash or credit toward book purchases. I usually take my books, DVDs, CDs and videos to the secondhand store first, see what they will pay for and usually take credit as they are more generous. My last trip there, they offered $12 cash or $15 trade. I took the latter as I found a cookbook I liked. Any items not taken by the bookstore then are donated to the thriftstore and used as a charitable deduction for my taxes.
Therefore, not only do you save money patronizing bookstores, you can supplement your book spending by bringing books, DVDs and CDs you no longer use and apply the cash or credit to buying other items you are interested in owning. Ideally, you can keep your bookshelves from being overwhelmed by getting rid of unwanted books and DVDs before purchasing new ones. Practice may not be so easy but eliminating the books, DVDs and CDs you no longer enjoy minimizes clutter. And if you take the cash, you can add it to a savings account for a future purchase. That makes secondhand bookstores a win-win situation!