Autotelic which means literally, "self projection".
It is our ability to fully put our entire energy and all our skills fully into whatever task is at hand. I sometimes use the phrase "active Reading" or "active viewing" to refer to the same general principle - when we read a book, putting ourselves in the place of the character, visualizing what he sees, smelling even the smells, we are having an autotelic experience. It makes any activity worth doing simply for the fun of it.
List of books: Autotelic