Amazon would be a good choice. You can list for free and they only charge you a fee (15%?) if you sell the item. Just look up the book you want to sell on amazon, and if they have it, click on the product page. On the right sidebar, below More buying options , there will be a sell yours here button. Click that, and it will start the process of getting ready to sell. ISBN not required.
First, since ISBN stands for International Standard Book Number, ISBN number is redundant. (I know you ll want to know that.)There are fees for any online seller, as far as I know. Are you determined to sell them yourself online, or do you want the best place to sell them, period? If you just want them off your hands in one go, take them to a used book dealer. Otherwise, abebooks.com is one of the main serious sources for used books from reputable book dealers, but I think individuals can set up accounts, too. Yes, eBay, I suppose, though then you will be relying on the chance of an interested buyer being around when you re trying to sell. Half.com seems to have a lot of individual sellers, as well. You can sell books through Amazon, too, but take a close look at their fees and shipping requirements.If you don t know much about books or don t have much expertise describing them, you re probably better off trying to sell them to a dealer or donating them to a library book sale.