What a wonderful setting for a game, reading a book as the stories plays out on the book itself.
My favourite part was actually right at the start where I read that the elf ran over and he actually did in the game. I wish there was more of that, like the enemies didn't wait for you to start the level but came automatically when you read that part.
I would have loved if the story adapted to your actions a little too, like if you barely beat the previous level it says something about how you struggled to fend off the previous wave.
The shooting was a little simplistic but I didn't feel that it detracted from the main feature of the game which was the active story.
I loved it, you've definitely got something great on your hands here!