1. Use PaperBack Swap. The site allows people to trade their books back and forth for free. All you pay is the shipping price. The site is used to trade not just paperback books, but hardcovers and even textbooks and audio books.
2. Go to the Gutenberg Project at Gutenberg.org. Not only are the books cheap, they are absolutely free. Many of the best books ever written are located on the site and are completely free.
3. Check out the local library for a free book box or a Friends of the Library store. Many libraries have both, so you’ll have a choice between some free books and some cheap books that have been dropped from the library’s collection. Every library eventually has to get rid of a few older books in order to house new titles, so check back often to see the new cheap books that are available.
4. Shop at the thrift store. Thrift stores have some great books available because many people don’t think to look there for books. Most of the time they have more boxes of cheap books in the back as well, so don’t be afraid to ask whether you can see the new arrivals.
5. Go to half.com. The site is often overlooked because of the popularity of Amazon.com, but half.com has many, many very steeply discounted books that are priced better than the books on Amazon. And like Amazon, the shipping prices are fixed by the site rather than by the individual sellers, so you always know how much shipping you will pay for your cheap book.