I highly recommend the Lucy and Stephen Hawking books starting with George's Secret Key To The Universe. My DS6 has read all three twice and can't wait for the fourth to come out in June! It inspired a great interest in physics!
Also, I second Grace Lin. We loved Starry River of the Sky and he is currently reading Where the Mountain Meets the Moon.
I am reading Inkheart aloud to him right now, but I'm a little worried it might get too intense!
Oh, and Brian Selznick. The Invention of Hugo Cabret! A family favorite!