As Apple's do-or-die deadline has come and gone for apps that offer users ways to purchase content outside of Apple's ecosystem, a number of prominent reading apps have begun to seed updates with the necessary changes. Those changes haven't exactly gone the way that most users would like, though—most have decided to simply remove their buttons and links pointing to outside content stores while continuing to not give users a way to purchase that content in-app.

Apple made the controversial decision earlier this year to begin putting pressure on the makers of content-based apps that sell further content somewhere outside of the App Store. It first started with the rejection of Sony's e-reader app and soon bloomed into a discussion of Amazon's popular Kindle app as well as a plethora of other e-book apps—Apple hinted that those apps should sell their content in-app or not appear in the App Store at all.

Apple quickly followed up with an official announcement about apps that sell subscription content (such as newspapers, magazines, and video sites): "Our philosophy is simple—when Apple brings a new subscriber to the app, Apple earns a 30 percent share; when the publisher brings an existing or new subscriber to the app, the publisher keeps 100 percent and Apple earns nothing," CEO Steve Jobs said in a statement at the time. "All we require is that, if a publisher is making a subscription offer outside of the app, the same (or better) offer be made inside the app, so that customers can easily subscribe with one-click right in the app."

Even though Apple eventually backed off on the same-or-better price requirement and decided that offering in-app purchases would be voluntary after all, the message was clear: if you're making money by selling books or subscriptions outside of Apple's ecosystem and simply using the App Store as a cheap delivery mechanism, you're either going to have to start paying up or stop advertising outside options. Apple set a deadline of June 30 for compliance with its new in-app purchase and subscription rules.

The company apparently extended its deadline through the end of July, because a plethora of app-makers have begun to make adjustments to comply, and most of them have gone in the direction of less convenience:

Amazon, perhaps the most high profile of the group, has removed the button taking users to the Kindle store on the Web from its Kindle app and has not added in-app purchases.

Barnes & Noble has made the same change to its Nook app, instructing users to open Safari and visit nookbooks.com in order to purchase new books.

The Kobo app (which is technically independent from Borders, though the brand is strongly tied with Borders' bookstore) joined the party over the weekend by removing links to the Kobo store from within its app.

The Wall Street Journal reported on its website that it, too, would stop selling content directly from within its iPad app to customers, though its app doesn't appear to have been updated yet. "People who download the app and want to subscribe will have to either call customer service or visit WSJ.com," wrote the publication.

Those are likely to be just a few of the apps that will send out updates this week to remove their linkage to outside content stores. There's another book reading app that appears to have mysteriously disappeared altogether, too: the Google Books app. Theories as to what happened have begun to run rampant, with the most reasonable theorizing that Google pulled the app in response to Apple's in-app purchasing rules, and others arguing that Apple actively kicked the app out of the store for violating its terms of service. Google did not respond to our questions about what happened to the app, so for now, our money is on the former.

Update: Google spokesperson Gabriel Stricker got back to us about the Google Books app. "We can't comment on this, but we can confirm that it's available once again," Stricker told Ars.