The Wall Street Journal says that before Amazon's purchase of the Goodreads service earlier this year, Apple was planning to possibly integrate the social reading-recommendation service into its own iBookstore. Apple and Goodreads, says the WSJ, had been talking for a year or more about combining Goodreads' social ratings for books into the iBooks app directly, but of course Amazon's purchase put the kibosh on any such team-up. Amazon purchased Goodreads for what could be close to $200 million, and purportedly plans to use the service and its user reviews to help sell e-books on the Kindle bookstore.
As for Apple, it's hard to say just what such a partnership would have looked like. Obviously Apple is willing to integrate partners in certain products, especially on iOS, where both Twitter and Facebook have seen fairly major social integration. But on the other hand, Apple's also very careful about mixing up brands, which is probably why any possible Goodreads partnership took as long as it did to come to light. Apple's seen a lot of success with iBooks, and so the company might be leery about including anyone else's content on that store.
Nevertheless, thanks to the Amazon acquisition, integrating Goodreads on the iBookstore is no longer a possibility. Currently, users can review books on iBooks in exactly the same way they can review apps in the App Store, and that solution may be good enough for Apple for now.