The latest features enable publishers to add instruction videos to how-to books, readings from authors and other add-ons to a work, much like special features are added to a movie DVD. Each of the books offered initially with the new Kindle app cost $10.
The audio/video segments of the books will only play on one of Apple's iOS devices. Amazon's Kindle e-reader does not support video, and the bookseller has not released a version of the audio/video Kindle app for the Mac or PC.
Nevertheless, by becoming the first to release such capabilities in e-books, Amazon has taken a step ahead of competitors, including Apple. However, it's likely the online retailer won't be alone for too long. None of the e-book releases appear to be exclusive to Amazon.
The new app is just the latest volley in the battle among sellers of e-books and e-readers. Last week, Amazon cut the price of the Kindle to $189, just hours after Barnes & Noble dropped the price of the Nook to $199. The e-readers had sold for $259.
The next day, Borders started bundling a $20 gift card with its Kobo reader, which sells for $150, but lacks a Wi-Fi and 3G connection available on the Kindle and Nook.
The price cuts reflect how booksellers are shifting market strategy from selling devices to selling more digital books, analysts say. With sales of e-books rising, the potential for higher profits is also increasing.
Apple is also adding to the pressure on e-reader vendors with the iPad. While the tablet-style computer costs considerably more, it can play multimedia, browse the Web, check email and perform other tasks associated with a traditional laptop. The starting price of the iPad is $489.