For each device, the update provides enhancements for viewing textbooks, with the 2nd generation Fire and the Fire HD 7" getting "X-Ray for Textbooks". This feature allows users to access the most important terms and concepts, with glossary definitions and links to relevant pages within books.
The update also provides enhancements for print replica textbooks across each device. Thumbnails of each page are now available at the bottom of the screen, and you can make notes and highlights in your books, as well as jump from one chapter to another.
Other improvements include "Time To Read", which calculates how much longer you have left until completing a book based on your reading speed, and each device can now read books with audio and video clips, too.
The update will be downloaded to devices automatically, but if you want to force the update to happen more quickly, you can initiate it from your Kindle and get it straight away.