John Derbyshire is very good in his 2001 Crusading They Went The deeds and misdeeds of our spiritual kin.

...the Crusaders were our spiritual kin.... Time and again, when you read the histories of this period, you are struck by sentences like these, which I have taken more or less at random from Sir Steven Runciman's History of the Crusades: "[Queen Melisande's] action was regarded as perfectly constitutional and was endorsed by the council." "Trial by peers was an essential feature of Frankish custom." "The King ranked with his tenant-in-chief as primus inter pares, their president but not their master." ...

No sooner had Godfrey of Bouillon been elected supreme ruler of Jerusalem ... than his first thought was to give the new state a constitution. This was duly done, and the Assize of Jerusalem — "a precious monument of feudal jurisprudence," ...What were their notions, their obsessions? Faith, of course, and honor, and then: vassalage, homage, fealty, allegiance, duties and obligations, genealogies and inheritances, councils and "parlements," rights and liberties....

...the virtues of men like Saladin rose as lone pillars from a level plain. They were not, as the occasional virtues of the Crusaders were, the peaks of a mountain range. The Saracens had, in a sense, no society, no polity. Says the Marquis to the Templar in another great Crusader novel, Sir Walter Scott's The Talisman: "I will confess to you I have caught some attachment to the Eastern form of government: A pure and simple monarchy should consist but of king and subjects. Such is the simple and primitive structure — a shepherd and his flock. All this internal chain of feudal dependence is artificial and sophisticated." Well, artificial and sophisticated it may have been, but in its interstices grew liberty, law, and the modern conscience.