You can find the app in iTunes, and in order to install it you will need to be running iOS 7 or later.
1. A brand new Themes feature to customize your Library and Home screen, including time-based themes that subtly change throughout the day.
2. Two new reading themes to choose from: try Cyan for a cool blue tone, or Charcoal for a darker experience that’s not quite as black as Night.
3. Overall performance improvements, and bug fixes for crashes happening with particular books.
4. Improved support for read-along books, page breaks, and more.