In an on-again, off-again romance with its readers, Scribd has adjusted its subscription model yet again. This time it returns to its original premise – unlimited reading for a flat monthly fee. Effectively immediately, Scribd subscribers can enjoy an unlimited number of books, audiobooks, news, magazines, documents and sheet music for $8.99 a month, following a 30-day free trial. But there’s one small catch: “restrictions on some titles may apply.” To find out what Scribd means by that, you have to read the tiny print in the Scribd Paid Access End User License Agreement.

This is one of many business model changes Scribd has made since its launch in 2013. Here are just a few we’ve kept track of:

October 2013: Scribd launches eBook subscription service

July 2015: Scribd cuts back romance catalog for being too popular

February 2016: Scribd to make big changes to subscription eBook service in March

November 2016: Scribd adds popular magazines to subscription eBook service

January 2017: Scribd pulls digital comics from digital subscription reading service

May 2017: Scribd adds newspapers to subscription reading service

So why the change back to unlimited reading instead of Monthly Read credits that were implemented in March 2016? According to Scribd co-founder and CEO Trip Adler, in an article on PublishersWeekly.com, the company had reached sufficient profitability to allow it to return to its original business model. Adler told Publishers Weekly that, in 2017, the company earned more than $50 million revenue with more than 700,000 paid subscribers with the number of subscribers growing by 50 percent each year.

Here are a few more interesting Scribd statistics since the company started:

One of the more controversial moves Scribd had made previously was reducing its romance catalog because super users were reading a significant amount of content, and Scribd needed to limit that usage to become profitable. Under the new (original) model, Scribd retains the right to limit titles at any point in the future.

Another reason for the change might be the change in the competitive landscape. In September 2015, the two-year-old Oyster Books shut down, as its founders headed to Google to work for Google Play Books. This occurred shortly after Entitle, another eBook subscription service, called it quits. Last month Google introduced audiobooks on Google Play, though it does not offer a subscription component, reports The Verge. In January, Walmart announced it would partner with Rakuten, a Japanese-based eCommerce business, on eBooks and audiobooks through Rakuten’s digital book business Kobo.

Insider Take:

The eBook subscription business is relatively new, and since its inception, companies have come and gone. Scribd is one of the few that stuck it out, and it has gone through many iterations of a subscription business model. Perhaps now – five years in – the company has found some stability which could lead to long-term sustainability. We think the market is still shaking out, much like the streaming video and music markets are, and we predict there will continue to be business model shifts and changes as companies find the right mix to suit all of their stakeholders (investors, subscribers, publishers, etc.)