Seattle-based Amazon.com CEO Jeff Bezos has responded by defending the company's practice of allowing the sale of used books -- and oh-by-the way mentioning that the complaining group is the "same organization that from time to time has advocated charging public libraries royalties on books they loan out."

The New York City-based Author's Guild is urging its members to eliminate links to Amazon on their Web sites, claiming that used book sales do "damage to the publishing industry, decreasing royalty payments to authors and profits to publishers."

Bezos said simply that the group's assertion "is not correct ... We've found that our used books business does not take business away from the sale of new books."

"...when someone buys a book, they are also buying the right to resell that book, to loan it out, or to even give it away if they want. Everyone understands this," he said in an e-mail distributed to sellers of used books on the Amazon site.

He also said that offering used books "is simply good for customers. It makes out-of-print books available and other books more affordable. Making books affordable is a fundamental good (as are libraries)."

He concludes by urging Amazon users to send e-mail to the executive director of the Author's Guild "explaining how the sale of used books actually helps the entire book industry."

The guild, which calls itself the nation's largest society of published authors, griped about the sales practice when Amazon first allowed used-book sales by its users two years ago.

Amazon is not actually in the used book business itself; rather, customers may sell their books through the online retailer. Amazon collects a 99-cent fee for each sale, plus 15 percent of the purchase price. No royalties are paid on used book sales.