This book covers a broad topic, and is therefore not extremely thorough. It still gives a good bit of useful text for its small size. Generally speaking the plates are good, but they have nothing on Angus McBride. The book covers the following topics, usually devoting one or several pages to each:
The Armies of Outremer (Christian territory centered on Jerusalem)
The Military Orders (like the Templars and Hospitallers, and some lesser known groups)
The Iberian Armies (El Cid and the Reconquista covers this topic in much greater detail)
Byzantine Armies (extremely brief)
Abbasid Armies (Armies of the Abbasid Caliphate of Baghdad)
Moorish Armies (the Armies of Islamic Spain)
Seljuk Armies (Turkish warriors during the Crusades)
Fatimid Armies (Egyptian Muslim forces)
Ayyubid Armies (those of Salah al-Din and the Battle of Hattin)
Mamluk Armies (Turkish slave mercenaries at the end of the Crusading period)
Plate Commentary