The first half of Medieval Warfare has four chapters on successive chronological periods — "Carolingian and Ottonian Warfare", "An Age of Expansion, c.1020-1204", "European Warfare, c.1200-1320", and "The Age of the Hundred Years War" — and two on warfare at the geographical extremes — "The Vikings" and "Warfare in the Latin East". These describe the large scale pattern of wars and some key battles and campaigns, but don't attempt a continuous narrative (a separate fifteen page chronology provides dates for battles and other events). The second half has chapters on particular aspects of warfare — "Fortifications and Sieges in Western Europe, c.800-1450", "Arms, Armour, and Horses", "Mercenaries", "Naval Warfare after the Viking Age, c.1100-1500", "War and the Non-Combatant in the Middle Ages", and "The Changing Scene: Guns, Gunpowder, and Permanent Armies".
Medieval Warfare is an integrated volume, not a collection of papers. The chapters overlap only a little and the contributors have only minor disagreements with one another (for example over how much Western European castle design was influenced by features encountered during the crusades). Obviously not everything can be covered in such a volume: perhaps the most notable absence is a treatment of logistics, from the immediate feeding of armies to the taxation needed to pay for them (though this is a topic touched on to some extent by almost all of the chapters).
Several of the chapters, and in particular the introduction and final chapter (by Keen himself), address the distinctive features of medieval warfare and its "boundaries" — the ways in which it differed from Roman and Byzantine warfare, and the changes towards the end of the period that started the early modern "military revolution". The volume as a whole gives a good feel for change within the period, and the slow and uneven pace of that change. There was, for example, no single technical innovation that made heavy cavalry, nor any single battle that ended its ascendancy. (In fact cavalry were a central part of most armies throughout the period, though it is unlikely they were at any point able to ride down disciplined infantry in a defensive position.) Another key theme, touched on by several of the chapters, is the shifting balance between the attacker and the defender in sieges and the effects of that on strategy.