In a press release from Apple, George R. R. Martin has this to say:
“We’re now entering a new period in the history of publishing,” said author George R.R. Martin. “The digital book gives readers the ability to experience all this rich secondary material that had not been possible before. These enhanced editions available only on iBooks include sigils and family trees and glossaries. Anything that confuses you, anything you want to know more about, it’s right there at your fingertips. It’s an amazing next step in the world of books.”
I've seen a lot of the television show but this looks like a great way to get into the complicated story told in the books. Can't wait to check it out!