The Norman Conquest is the single most important event in English history. On this invasion and 'regime change' pivoted the second millennium of English history. This is well recognised, what is not is how long and hard the English people fought to deny William 'the Bastard', Duke of Normandy his prize. Rather than being the smooth transition peddled by pro-Norman historians, the Norman conquest was a brutal and violent takeover by an army of occupation. Unknown thousands of rebellious thegns resisted the Norman regime, the most famous being Hereward, but there were plenty of willing collaborators among England's clergy, who pushed for William to be crowned king. In return he let them retain their sees and abbacies, as well as the vast tracts of land. Peter Rex tells the whole story of the conquest of England by the Normans from its genesis in the deathbed decision of King Edward the Confessor in January 1066 to recommend Harold Godwinson as his successor, to the crushing of the last flickers of English resistance in June 1076. (Amberley Books)
The problem with any such book is that the bias, in primary and secondary sources, is towards military action and events. However, Rex's short appendix on conquest castle does show a modern understanding of the complex functions of castles.