The official Kindle app for iOS (universal, free) was updated a few minutes ago to introduce a new feature recently launched on the physical Kindles: real page numbers. Page numbers (currently available for thousands of Kindle books, more coming soon) allow you for instance to make proper citations that other people using Kindle can follow along. It’s a very welcome addition to the app.
The 2.6 update also brings Google and Wikipedia lookup without leaving the app, reading percentage for iPhone and reading progress on the iPhone and iPad Kindle homescreen through the list view.
Kindle 2.6 is available as a free update here. The app was last updated in January to add features like multitasking and iTunes file sharing support.