Selling books

Today, I got a box of books I've been trying to sell down to go through and sell. I had read about www.cash4books.com. While most of my books are paperbacks, Cash4Books takes very few paperbacks and has a strict policy on the condition of books. Of the books I inputted into the website, they would buy none. I will check back later with different books, maybe some text books I know that I have in a box somewhere.
In the past I've used Half.com in the past and have done pretty well, but with Cash4Books they pay the shipping right off the bat, you don't put out for the shipping at all, unless you choose not to print the mailing label they offer you.
My sister-in-law uses www.amazon.com to sell books, so I'm going to keep hunting and will report back later.