Back in the MS monopoly days, there were a ton of things people wanted to do where they had no choice but to buy Windows if they wanted to do them. Today, there is very little that people do which requires an iOS device. Apple has many closed features (the App Store, iMessage, iCloud) but open equivalents are available. Almost nobody is buying an iPhone because they need an iPhone in particular to do something. They're buying iPhones because they need a smartphone, and they prefer an iPhone.
I am very much not a fan of Apple's approach here, I just don't see anything illegal about it.
Apple already got in trouble for price fixing - a violation of the Sherman antitrust act. https://en.wikipedia.org/wiki/United_States_v._Apple_Inc.
Related to iOS and competition within it, see
http://fortune.com/2016/06/30/elizabeth-warren-apple-google/
http://www.thehill.com/opinion/op-ed/272399-time-to-prosecut...
Hopefully more to come from me on this topic...my channel here. https://medium.com/@ryanpollock
In this instance Apple and the other publishers probably did so specifically because they didn't have a monopoly on ebooks.
Sure, and equivalently Apple has a 100% monopoly on Apple devices. How does that make sense? One problem with anti-trust laws is that the market is not well-defined. Is the relevant market Apple phones? Smartphones above some price point? Smartphones at a price point? All smartphones? We can always pick and choose to make it seem like a company has a monopoly.
By virtue of Apple integrating the operating system with hardware, iOS has a defacto 100% monopoly on devices compatible with Apple's Ax series chips (e.g. A9 in iPhone 6s). There's nothing illegal about that.
The market for Ax series devices is now larger than the Intel-compatible PC market was at under consideration during the Microsoft antitrust case.
The question then is whether Apple's policies stifle innovation and harm consumers. I think the answer is "yes".