Heat waves aside, this last weekend has proven to be a fairly rough one for e-book sellers. In spite of backing off a bit from its initial demands, there have apparently been some major changes afoot in the iOS App Store, with a number of apps scaling back access to their online e-book markets or being pulled from the store altogether. Kobo, one of the former, told The Wall Street Journal (which also reported on its own iOS woes) it was informed on Saturday that it needs to stop selling books through its app. The Google Books app, meanwhile, has been removed altogether, though Google has yet to comment on the matter, possibly revamping the app to comply with the stricter rules. While the adjustments will certainly be a nuisance for the companies involved, selling books through Apple devices will not be an impossibility, so long as customers can still access the markets through Safari.

Update: You can now add Amazon to the list as well. The latest version of the Kindle app removes the Kindle Store button that previously allowed you to purchase e-books on your iOS device.