eBooks, electronic books available on various devices, are already a lot and first of all these books may be multimedial. Multimedia is indeed the right term, because beside the format book itself any kind of media may become integrated, images and even updated images, music and video. Rather there are new genres coming up like social news clipping or transmedia storytelling.
In the case of ebooks, which today may be published by everyone, Booktrack has launched an application to integrate audio into ebooks. To keep and extend the fun of reading the sound is played synchronous to the text and may be turned on and off. The kind of audio is flexible, it may be music, effects or just a background. For more read this article and visit Booktrack.