I just took my last history class last semester, and was disappointed because we did not spend much time covering Prussia - a country that I have been interested in for some time now. I would like to read about the social/court lives of the aristocracy, or perhaps something about the Seven Years War. I really enjoyed the movie Barry Lyndon, and it's depiction of Prussia. Also, I have always been a little confused about the political situation of Prussia, Brandenburg, and the Hohenzollern family. How exactly did Prussia form and break from the Holy Roman Empire? So maybe something about the rise of Prussia would be good, also.
The Iron Kingdom by Christopher Clark is an excellent overview. http://www.theguardian.com/books/2006/sep/09/featuresreviews.guardianreview10
Although I do find it a bit odd that Clark or his editors Anglicized all the names of the Prussian kings. Fredrick instead of Fredrich, William instead of Wilhelm and so forth.
A list of books in english is quite limited for semi-obvious reasons but there are still some great options. I would recommend a duel of nations and a duel of giants by david wetzel. I took a class with him this fall, not only is he incredibly knowledgeable but also an extremely engaging lecturer. I will also link his itune lecture podcasts, which are definitely worth a listen, though he repeates himself a lot because everyone is taking notes.
http://www.amazon.com/Duel-Nations-Germany-Diplomacy-1870-1871/dp/0299291340/ref=pd_bxgy_b_img_y
https://itunes.apple.com/us/itunes-u/history-162a-001-spring-2012/id496141591?mt=10
Second, chapters in Struggle for the Mastery of Europe by AJP Taylor cover prussia and european history extensively and is extremely readable.