I used to sell used books, mostly textbooks on Half.com, an eBay subsidirary. Half does a decent job for me and their commission is reasonable (about 10%?). But I have not enjoyed much success selling books there lately. It could be one of the two reasons: My books are unpopular; Half.com is not popular anymore.
I started to use Amazon Markplace instead. Its commisson is much higher, theSunsFinancialDiary says its commisson for book is as high as 18%. But I am OK with it as long as it sells. My rationale behind this is: book does not increase value as time goes, as matter of fact a textbook loses most of its value when new edition come out; if I don’t read the book for a year, I probablly won’t read it at all, so why not convert that into cash? Same thing can be said for some unused household items.
On business side, Amazon increasingly looks like a mall (like eBay), instead of a store (like Wal-Mart). Smart move I think.