Have you tried joining paperbackswap.com or frugalreader.com? You can swap your books for others and all it costs is the media mail postage when someone requests a book you have listed. For every one you list and mail, you get a credit to order one. You also get a credit the first time when you list I think it is 10 books. I have really enjoyed it.

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"If you can read this, thank a teacher."