Richard Wolff is the leading U.S., Marxist Economist. I recently came across this nearly two hour presentation, from a couple years back, in which he reviews and comments on the development of socialism from feudal times to present day. It is doubtful there is any better informed person on Marx alive today than Wolff. If you have the time, you should find this talk both enlightening and fascinating, particularly if your knowledge of Marx's contribution to economic thought is cursory, as mine was. This post may not belong so much in the "politics" as in the "economics" forum, so I hope the moderator will relocate it as they think appropriate.