I don't know how I came to this site, but has hundreds of short interactive presentations about many different topics.
Can't be compared to iBook 2 in terms of UI, but the simple content explanation and the way it's disposed (not linear like a normal book) is excellent.
Can't be compared to iBook 2 in terms of UI, but the simple content explanation and the way it's disposed (not linear like a normal book) is excellent.