The illustrations are wonderful. The first part of the book has a lot going for it and I love this format Selznick has created. He is ambitious. Big themes, lots of interesting ideas... I can't wait to see what he does next.
Unfortunately, I began to loose interest as the separate stories collided. I have to say that I agree with those (few) readers who were disappointed by the story and the writing itself. Eventually, even Ben, the main character, did not come across as fully developed. And the story in pictures, once it came together with Ben's story, did not seem vital. I expected a coherent whole to form, but that did not happen. Too many nagging questions about characters and their motives, too much coincidence in the plot, and a denouement that was not earned (too much telling instead of showing).
I think it would be very interesting if Brian Selznick and David Mitchell worked on a project together.