Oh. My. Gosh.
This app is part storybook, part game, and part animation. Wonderful writing and animation, plus the interactive bits are well-integrated and enhance the story rather than distract from it. A question I posted in Twitter a while back prompted much discussion on Twitter and Google+ about what exactly makes a children's ebook (vs a game), and I'm nearly finished compiling people's comments into an article...I definitely have to mention Moonbot's book app!
Anyway, the story's about a book-obsessed fellow who gets swept away by a storm and ends up in a country house filled with bookish fun. See the trailer above for more info.
Simon & Schuster is publishing a book based on the app/film, and Dreamworks is coming out with a movie in 2012.