"An Austrian Perspective on the History of Economic Thought" by Murray Rothbard
This was great because of the history lesson packed into a book that's mostly about economics. I didn't realize how libertarian the economic thought of the east was until I read this book. I also appreciated the focus on economics before Adam Smith since I knew only about Aristotle and St. Thomas Aquinas's contributions prior to reading the book. Rothbard's take-down of Marx was both thorough and satisfying.
"City of God" by Augustine of Hippo
The history lesson here was helpful as was the perspective on how the church should view the state though I should have invested more money in a better version for Kindle. The version I had was filled with grammatical mistakes due to the poor translation to the Kindle format.