Sounds like a great product and I'd bet it will be a huge success. Remember when the iPad first came out the top selling paid "app" for the first 2-3 months was

Sounds like a great product and I'd bet it will be a huge success. Remember when the iPad first came out the top selling paid "app" for the first 2-3 months was the "Elements" ebook. It was a much simpler version of what Gruber described, but it sold like hotcakes. After you buy your $500-800 tablet, you want some software to show off how cool it is and a few well produced nature/cook/science books that have physics based demo features will do that perfectly. The comment about content being hard to product is right on. My guess is that they will publish just a few books a year, but they will be amazing looking and beautifully produced.