Evolution takes a great deal of time and happens over generations rather than lifetimes.
The definition of a ‘book’ will not evolve until paper copies of books cease to be published. Long player vinyl records are no longer mass produced for music but the notion of an album still exists on iTunes even through the physical product is almost dead. A collection of songs in a particular style will continue to be defined as an album as will a collection of words on a theme continue to be defined as a book.
What will evolve however is the notion of a story in fiction or a designated expert writer in non-fiction. Around a camp fire or when reading to children many people can contribute to a story orally or change stories that they tell. Digitized fiction books will take this ‘playfulness’ we have with the creation of stories and provide more ways to play with a story. Whereas digitized non-fiction books will result in their not being one single expert but a number of contributors who could all be accessible to the reader. In much the same way as the springbeyondthebook project.
A book will remain a book as it exists in its current form but the notion of a story or non-fiction content will evolve in the future.