Apple has updated its iBooks app for the iPad and iPhone, adding a number of features that weren’t there for launch.

Having already served up over 5 million iBooks, that's 2.5 books per iPad for anyone counting, Apple are already claiming that it is a huge success, although it is worth pointing out that number includes the free Winnie the Pooh book everyone gets when they download the store.

The new iBooks app, due out later this month, will be getting the ability to add bookmarks to pages as well as the ability to access your own PDF files using the app, something that was a criticism by many when it first launched alongside the iPad in April.

For PDF files, Apple CEO Jobs says that navigation will work like regular iBooks and that means you'll be able to add bookmarks, highlight text and check what certain words mean.

The new iBooks app, which has also been promised for iPhone in the latest version iPhone 4.0, will be available at the end of the month presumably in time for the new iPhone.