I have a pile of books I want to get, and most are at least 50% less than the regular Amazon price, albeit used (but in good condition, according to the sellers), via Amazon Marketplace.

Any problems with Marketplace, or is it reputable for the most part?

I'd say it's a bit better than eBay and maybe pretty similiar to Half.com. Unfortunately unlike eBay, you can't get a picture of it to base the condition on and you have to take their word.

I ordered a used book off Amazon a while back. Once the three weeks had passed and I had not received it, I emailed the guy. "Oh, we'll look into it". Several days pass, no response. Second email, same response. I filed a complaint with Amazon and when they went to him with asking what the deal was, the response was that is was never in stock to begin with.

I use it all the time, most of my books are new or in great shape. Read the descriptions carefully, look at the sellers feedback and don't always automatically go for the cheapest book. Out of the 30+ books I have bought only one wasen't very good as it did not come with a dust cover.

I have saved a lot of money buying books on Amazon's marketplace. As suggested, make sure you check the feedback and the description. I usually only consider sellers with feedback at least in the high 90's. You used to be able to get the A9 discount on marketplace purchases too, but Amazon got rid of that. Also, factor in shipping costs. I think shipping is usually $3.49 per book on the marketplace. If the total price with shipping is not much more than Amazon with free shipping, I usually order from Amazon.

Don't forget about buy.com's $10 off $30 purchases with the google checkout. I have placed several book orders already.

I like it. I have had far better luck with them over half.com and eBay for books.

I've used it lots for books, DVD's, and CD's. I've only had one bad experience, but have had dozens of good ones. Usually the books are in almost mint condition even when used. DVD's the same.

I use it occasionally, and have always been satisfied with it.