Having recently read Iron Kingdom: The Rise and Downfall of Prussia , what I found particularly interesting was the century between Napoleon and WWI- specifically German Reunification, and the political manoeuvres used by Bismarck to achieve it.
What are some good books on this period?
Sounds like William Carr's The Origins of the Wars of German Unification is precisely what you want. It's entirely the political and social mechanisms that led to, well, German Unification. It's my favorite work on the matter, I recommend it before touching anything else.