Here's another article on this (both confirm that it will also apply to ebook store apps):
http://www.thebookseller.com/news/ap...y-e-books.html
It seems Apple are tightening the screws still further, and contrary to our earlier understanding, which was that an app like the Kindle one could offer two methods of purchase, now it appears that only in-App purchasing will be allowed.
You can buy through the browser, but the app can't trigger it.
I suppose the obvious response by Amazon, given that it appears they can make no profit on the app (at least under Agency pricing), would be to turn it into a pure reader and remove the store functionality. They may even have to get it made by a third party to get round the rules!
Graham