One of the authors of The Spiderwick Chronicles, Tony Diterlizzi, has just released his latest book, The Search for WondLa. He's done something rather interesting with the paper edition of this book. If you have the book and a computer with a webcam, you can use the book to access a map of the world that the book is set in.
While the demo video looks cool, I want to see how well this works with a smartphone.
Watch the video, and you'll see it doesn't work quite so well with a webcam. A smartphone would put the camera and screen in between the user and book, and I think that would work better.