Goodreads used Amazon’s public Product Advertising API to source basic book data like title, author, page count and publication date.

Goodreads’ situation illustrates the risks of building a site around any retailer’s API, since that retailer can change its terms at any time. Amazon’s Product Advertising API license agreement has not changed since April 2011 but “the terms now required by Amazon have become so restrictive that it makes better business sense to work with other data sources,” the company told me.

Specifically, Goodreads finds two requirements of Amazon’s API licensing agreement too restrictive. Amazon requires sites that use its API to link that content back to the Amazon site exclusively—so a book page on Goodreads would have to link only to its product page on Amazon, and not to any other source or retailer. Goodreads links to many online retailers. “Our goal is to be an open place for all readers to discover and buy books from all retailers, both online and offline,” the company told me. Amazon also does not allow any content from its API to be used on mobile sites and apps.

The changes take place January 30. Goodreads’ new data source is book wholesaler Ingram. Goodreads will pay to license data from Ingram, and will supplement it with book records from the Library of Congress and other sources.

Goodreads stresses that most book records will be safe: “Not a single review, comment, shelving, or rating will be lost in this transition. That’s the most important thing—your data is 100% safe.” It’s calling on “Goodreads librarians”—users who’ve applied for and received permission to edit data in the catalog—to help verify data for some titles that may be deleted otherwise. Here are the books that need to be “rescued”—including many foreign-language titles.

Books that are only available through Amazon, like Kindle editions ands self-published Kindle books, have no alternative data sources. “We anticipate keeping these, and will bend over backwards for all our authors who publish via Kindle to make sure their readers on Goodreads have a smooth transition,” the company says.