You are entering a minefield where there is no safe path!

Take for example one of the first links that comes up on Google when searching feudalism, from a university site, https://faculty.history.wisc.edu/sommerville/123/feudalism.htm . It summarizes feudalism as:

The very definition of feudalism is debated, but roughly speaking a feudal society is one where:

• Land is held in exchange for service

• Obedience is rendered in exchange for protection

• Society is hierarchically ordered with a military class of highly-trained and expensively-equipped warriors supported by a mass of peasants who provide labor and are tied to the land.

The problem is that no historians actually agree on this definition anymore, and in fact many argue that the above had very little to do with how society functioned in western Europe between CE 500-1000. We find far more exceptions to the above than we find concurring sources.

Pushing the problem further, I'll quote from myself as found in the links provided by in this thread by /u/OldWorldGlory :

Feudalism is an abstract concept, it means different things to different people. To some it might mean a pyramid structure of political and military power, from king down to serf. For some, it might be a word for the expression of power, so feudal means 'lords' treating their 'serfs' poorly. For others feudal might be focused on vassalage, the ties of a lesser to a greater noble and the implicit obligations. For others still, it might also included fiefs, with their implied expectation of military contributions. And to economists, feudal might mean the relationship of peasant and lord to economic production.

Now, what you have been hearing in Wolff's video is 'economic feudalism', or more often referred to as 'Marxist-feudalism'. This usage of feudalism skirts some of the above controversies of 'feudal' political and social organization, and strictly focuses on the economic mode of product (the fundamentals of the medieval economy), which were lords extracting surplus production from laborers via threat of force. Marxist feudalism itself poses a number of problems (and Wolff repeats several of them), but it's less controversial because it restricts the discussion to points where there is broad agreement among historians. Its major problem is that it comes burdened with a certain Marxist historical philosophy about economic relations being the 'motor of history' ('class struggle'), about the nature of 'class crisis' driving historical change, and a view about 'history as progress of man'. That said, we can still very usefully use the diagnostic tools even if we don't believe the suggested cure; but we should be clear that Wolff's explanation in the video is less historical description than economic analysis focused on Marx's belief in revolutionary crisis.

Unfortunately medieval historians of the last 20 year have focused less on medieval economy, with Chris Wickham being one of the few carrying the torch. Otherwise you'll need to go back a bit to writers like Rodney Hilton, Michael Postan, some of Georges Duby's works.

If I were to recommend on book about this, I would go with Georges Duby's The Early Growth of the European Economy: Warriors and Peasants from the Seventh to the Twelfth Century. It can be found used online really cheap, and its still a key reference work while being very readable.

This is a very simplified discussion of Marxist historical materialism and it is a particularly tricky thing to explain as Marxists operate a very different interpretation of feudalism than most other historians. It allows them to say stuff like 'there were no slaves in the Middle Ages'. There were, of course, but Marxists of this type only care if the chief mode of production is by these slaves (which it was not). Serfs pose a more difficult phenomena, there is currently great debate around the meaning of free and unfree especially in the period leading up to 1000. Before this point another, slightly in jest, label has been proposed - 'slerfs'. Then there is the timing of the 'feudal' period. This is, according to the lecturer, 500-1500 (except when it suits him to extend that to 1789 and the French Rev. but whatever - it's an introduction). The picture he is painting is one of clearly defined epochs between the period of Master and Slave, the end of the Ancien Regime and feudalism, and the beginning of modernity. This is the historical materialist theory, clear epochs which all pour forth into modernity and, ideologically speaking, will lead to the rise of the proles. This is not a historical interpretation it is an economic one. Feudalism exists for Marxists because they define the world in terms of one in which a surplus is generated by peasant labour equals feudalism. In the linked posts, however, I was primarily discussing the sociological and legal aspects of feudalism. For a useful overview of feudalism's various definitions and features see this excellent encyclopaedia entry by Levi Roach.

You might be interested in posts from the FAQ section on Feudalism:

• High and Late Medieval Europe 1000-1450
  ^(14 Feb 2014 | 376 comments)
  ^(/u/idjet describes the common definitions of feudalism, criticisms thereof, and some of the ways that people lived and worked in Late/High Medieval Western Europe.)

• AMA "Feudalism Didn't Exist" : The Social & Political World of Medieval Europe
  ^(26 Jul 2014 | 170 comments)
  ^(/u/TheGreenReaper7 & /u/idjet elaborate on the existence of lack thereof of Feudalism in Medieval Europe, as well as alternative interpretations of Medieval political systems.)

You can ask followup questions by posting your questions in the comments with experts tagged to direct questions to them.

Thank you all, I have started to look at the links....