There were a lot of complex and convoluted ideas thrown in here; but the plot was fun, the tension consistent, the pace acceptable, and the revelations surprising.
My only real complaint might be how little we see of Einstein's daughter. She seemed an interesting character and I would have liked to see more of her. Unfortunately, with there being 35 kidnapped children in all, my chances of seeing her play a large role in any future book are slim.
Another well done entry for the series.