A comment from Apple spokesman Tom Neumayr, via AllThingsD (Apple Fires Back at the Feds, Amazon):
The DOJ’s accusation of collusion against Apple is simply not true. The launch of the iBookstore in 2010 fostered innovation and competition, breaking Amazon’s monopolistic grip on the publishing industry. Since then customers have benefited from eBooks that are more interactive and engaging. Just as we’ve allowed developers to set prices on the App Store, publishers set prices on the iBookstore.
Read more at AllThingsD.