Big changes are underway in the e-book app world. Since Saturday, iOS (Apple’s operating system for mobile devices such as iPhone, iPod touch, and iPad) apps for Kobo, Barnes & Noble’s Nook, and Amazon’s Kindle have been updated to remove e-bookstore features and links to external online e-book stores such as kobobooks.com. The Google eBooks app, which has been available in the U.S. App Store since December 2010 (although unavailable in Canada) has been removed from Apple’s App Store and iTunes entirely.

The updates follow Apple’s weekend warning to Kobo regarding compliance with latest App Store rules. The Wall Street Journal (which will soon remove all purchasing options from its own app) reports:

Mike Serbinis, Kobo’s chief executive, said Apple told Kobo Saturday that it could no longer operate its digital bookstore from its Kobo apps and had to stop selling e-books directly through them. Kobo subsequently altered the apps so that they no longer sell digital titles.

Now Kobo customers who want to buy digital books via their Apple devices will have to visit www.kobobooks.com via Apple’s Safari browser to make their purchases, a potentially more laborious process for customers used to buying e-books directly through a Kobo app. Customers will continue to be able to access and read Kobo-purchased books from their library on various Apple devices.

Apple first announced the new App Store rules, which strictly forbid in-app links redirecting customers to online e-bookstores, in February and set a June 30 deadline for compliance. Apple’s enforcement of this policy comes as a surprise since the tech company dropped some of their original conditions last month, and the cutoff date came and went without much change to existing apps. From WSJ:

Apple in February laid out new terms for companies wanting to sell digital content via its devices. Apple said that companies selling digital media, including books, needed to make that content available for sale via an app, rather than through a link within the app to an outside website. As part of the change, which was aimed at giving Apple more control over the business, Apple said it would take 30 per cent of each sale.

In June, Apple appeared to relax those rules in content companies’ favour, giving them more freedom over pricing and selling their content. Apple dropped its requirement that any content sold outside the App Store also had to be available inside the store at the same price or less, with Apple taking its cut.

The updates to these e-reading/e-bookstore apps mean content providers maintain ownership over customer information and avoid cutting Apple into 30 per cent of a sale. Ultimately though, it makes purchasing e-books for Apple devices less user-friendly, which, unless Quillblog is mistaken, is a big part of the appeal of Apple devices and e-readers in the first place.