Goodreads, the social network for reading and reviewing books, had to make a change this month. It moved away from its main source of book data, the Amazon Product Advertising API, citing its "many restrictions." It completed the transition to Ingram Book Company's data today, and it also draws from other open data sources such as libraries. The transition went smoothly, but Goodreads did lose some data. "Fewer than 2% of our 7 million users have books currently affected," Goodreads says.

The problem most visible to users will be missing cover images. Goodreads is in the process of uploading replacements. One percent of Goodreads books will appear blank, listed as "Unknown Title" and "Unknown Author," while Goodreads looks for a new data source for them. There's a great lesson here about building a business on top of a competitor's API, but Goodreads has made the switch in the nick of time.

Why Amazon Stopped Working for Goodreads

Goodreads has risen farther and faster than its competitors, LibraryThing and Shelfari, except by one measure: Amazon bought Shelfari. This happened over three years ago, and Amazon has yet to do much with Shelfari. It launched Kindle Profiles last year without a Shelfari in sight. But to the extent that Amazon has invested in a social network for readers, it and Goodreads are competitors.

But at the end of the day, Amazon is a retailer and Goodreads is not. Goodreads built its business on Amazon's product advertising API, so there was no problem on Amazon's end. That API required Goodreads to link books back to Amazon, so Amazon made money and Goodreads got a cut, as well as a wealth of images and data about its millions of books.

But the usage requirements of the API are picky. The most troublesome requirement is that clients cannot, "without our express prior written approval, use any Product Advertising Content on or in connection with any site or application designed or intended for use with a mobile phone or other handheld device." That's no good. Goodreads has mobile apps, and those are more convenient for checking in while reading a book than a desktop site is.

The other key restriction is that Goodreads couldn't link to competing bookstores while using Amazon's API. Users will notice that Barnes & Noble is now the most prominently displayed book seller on Goodreads, and Amazon sits in a drop-down menu with a bunch of other sites.

Why Goodreads Will Be Fine

Shelfari may have the benefit of using Amazon book data to its heart's content. But Goodreads has built a thriving social network on top of its book data, and it offers much more to users than the competitors. In addition to original content, like interviews with authors, Goodreads makes for a great Facebook Timeline app, so Facebook users can turn the books they read into life events.

But even within Goodreads itself, there are great book recommendations using true reader sentiments, not just purchase and browsing history like Amazon uses. Goodreads acquired Discovereads last year to build a "taste engine" on top of its users' data.

Goodreads also offers a social reading API of its own, so developers can access social data, reviews and discussions. For Goodreads, the books themselves are just the backend. While Amazon is surely a wealth of book data, Goodreads can repair its library on its own. It will pay license fees to Ingram, the largest U.S. wholesaler of books, and it will fill the gaps from libraries and other open data sources.

This teaches a lesson about building a service on top of another company's data, especially one that might want to compete with you. But for the long term, these growing pains will be well worth it as Goodreads makes its way independently.

Do you use Goodreads or another social reading service?

Lead photo courtesy of Tatiana Popova/Shutterstock.