When I found myself overrun with books, I went to two used bookstores and this is one of them.
They have a great selection of used books and offer a generous trade in/sale policy and if you're book is in decent condition and not one of the books saturating the market, they'll more than likely be able to make a deal with you.
I've also been to a book reading here, so you can meet authors of some great new books also.
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