It may have escaped public attention that we now have
[[Wikipedia:Book sources]],
the text of which is fetched whenever a user clicks an ISBN number in an article (instead of the previous, hardcoded list of sellers). The text "MAGICNUMBER" on that page is replaced with the ISBN number the user is searching for when it is displayed, so you can add "magic" search links to any bookseller you like.
Hopefully, this will allow us to address concerns regarding specific booksellers. I have started by adding links to all the listed sellers, so that you can conveniently read the article about Amazon.com before buying anything from them. We should also have library catalogs listed here, and maybe a note on the general problem of using ISBNs to locate books.
Regards,
Erik