Apple has updated iBooks, the iOS software that lets you read e-books purchased through the iTunes Store on an iPhone, iPod touch or iPad. The new 1.1.1 release is available for download.

The update sports several improvements, according to Apple, including the ability to double-tap an image to view it in greater detail; use books that include audio and video; look up definitions to English words inside books without a specified language; and better performance when viewing PDF-formatted e-books.

Apple has also fixed a bug that could cause some book downloads to not complete, and has included other undefined “stability and performance improvements.”