In my opinion (seemingly shared by virtually anyone else who has read his work), Harold Berman is one of the truly great legal thinkers of the 20th century and Law and Revolution is one of the great masterpieces of legal scholarship. Berman has been one of my two most significant intellectual influences, along with Hayek. You can see his influence here and here and you can see my effort to combine the thoughts of the two of them here. Unfortunately, my impression is that Berman is largely unknown to most.
John McGinnis has a post (the first of a series) on the Law and Liberty website on Berman. Check it out. This one is short but you’ll want to follow the series.