I'm sure that The Civil War by Shelby Foote has been recommended to you. One of the best history books I've read focuses on trade. A Splendid Exchange by William Bernstein. I'm not sure how spoilers are done in non-fiction, but it was enlightening to read about the trade between India and the Roman Empire and also the trade between the Arab world and China. There is a kindle edition.
http://www.amazon.com/Splendid-Excha.../dp/0802144160