Lincoln's Code: The Laws of War in American History

With a focus on the Civil War and Lieber's Code, this book covers in effect 1776-1914. It is not fully comprehensive but it's approachable to the lay reader and has a lot of good stuff. Jack Goldsmith liked it too. Overall, a continual theme is the pragmatic spirit of the enterprise, if resulting in some idealistic ends. Some very good vignettes.