Reddit mentions of England Under the Norman and Angevin Kings, 1075-1225 (New Oxford History of England)

Ok first things first we need to define our field a bit. The Anglo-Saxons were not by any strict definition 'feudal'. "Feudalism' as an economic/political system only properly appears in England under the Normans after the conquest in 1066. So I'm going to give you sources that point towards that.

• Joseph Strayer's Feudalism is a nifty little (47 pages of analysis) book with a great selection of primary documents at the end. The caveat, it is nearly 60 years old and so it is rather simplistic and out of date. That being said the documents are still very much primary and may be of help.
  
  
• Robert Bartlett's England Under the Norman and Angevin Kings is a very not small book. It is, however, exaustive and up-to-date and so might prove helpful. It has chapters on everything from the actual political landscape to Lordship and Government, Warfare and even Faeiries.
  
  
• English Historical Documents is a series of works which combine numerous primary sources. Volume 2 is probably the best place to look.
  
  
• The Internet Medieval Sourcebook also has a wide variety of primary documents worth looking at which don't even require a trip to the library!
  
  I hope that is helpful. One last thing to remember about 'feudalism'. It is not a clean system and it is not a neat pyramid. It is a constant struggle for privilege and power. Kings want to get as much as they can from their vassals (service, payments, etc.) while giving up as few privileges/rights (land, support, protection) as they can. The same is true for the Vassals.