I need to purchase some used textbooks for one of my math classes. The book I used last year just isn't cutting it. I dug through a closet and found a few copies of an old text that was used a few years ago, but I don't have enough. I got permission from my admin to see if I can find and buy some used copies (it's old-copyright 1985, but it is a solid text, and both the high school math teacher and I agree that it is a much better option than the newer, less rigorous text). I have checked half.com, but I wonder if anyone knows of another site that sells used books reasonably?