Here are some other books by D. Nicolle that are worth having:
Crusader Warfare: Byzantium, Western Europe and the Struggle for the Holy Land 1050-1300 AD (v. 1)
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Crusader Warfare: Muslims, Mongols and the Struggle Against the Crusades 1050-1300 AD (v. 2)
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Medieval Warfare Source Book (v. 1)
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Medieval Warfare Source Book (v. 2)
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Victory in the East: Military History of the First Crusade by John France
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Crusading Warfare, 1097-1193 by R.C. Smail
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Here are three translated sources (Latin, Greek, Arabic) from the era at a fair price:
The First Crusade: "The Chronicle of Fulcher of Chartres" and Other Source Materials
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The Alexiad
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An Arab-Syrian Gentleman and Warrior in the Period of the Crusades
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There are many more translated sources, but they can be quite dear.
Chris