Future

I like your idea of the spotify play list for a book or for a series of work. Little bit like High Fidelity - Nick Hornby?
but you could listen while you read.
But it is perhaps difficult to adapt the length of text so that the songs change exactly when the reader changes pages or the chapters???
(Could perhaps work like in school, many years ago, watching slides, a beep on the speaker track tells when it is time to change to the next slide)

Also Janis idea of implementing GoogleEarth (or GPS-noding) could be fun to play with in some ways.
I have heard that fans to Mankells books arrange tours in the actual towns and landscape where the story takes place.
Interesting to build on this ideas...

I think that CD-books and mp3-books will grow very fast in popularity, listening to a book read by an actor is very good way for people on trains, and there is services arriving that stream a book to your phone (listen to many books for a monthly fee)

The book does not really need to be printed on pages anymore, it could perhaps be easier to edit and reedit, like the wiki-pedia-system perhaps? I heard about some novel attempts using wikis, but dont think they became popular enough to spread.

Does all new cell phones have GPS-functions? Listen to a book, with background music, and GPS-coordinates arrive sometimes, so you could walk or ride your bike there if you would like to follow the story more vividly

???