I’ve just started reading a very interesting draft book by David Friedman, called Legal Systems Very Different From Ours. It includes chapters on “Gypsy Law,” “Amish Law,” “Jewish Law,” “Islamic Law,” “Somali Law,” “Athenian Law,” “Irish Law,” “Chinese Law,” and “Plains Indian Law,” as well as a number of analytical chapters connecting these legal systems. The entire draft is posted on Friedman’s website, and he apparently welcomes comments.