Abebooks UK lead the field with a rating of "89% for overall satisfaction and were praised for how easy it was to find products on their site."
That seems pretty high to me. We do a lot of ordering for customers, and one out of every three orders arrive quickly and without hassle. More often than not, books are "out of stock," or we receive a book that is totally different from what we ordered. This happens a lot using Amazon, as they are still working out the kinks of their ISBN/ASIN title matching system. Usually it is an issue with large print / audio book / book club edition substitutes. Overall, it is good to see these numbers. Happy customers come back.