The Art of War in the Middle Ages 378 - 1515

Oman provides an excellent, well-researched look at the arms, tactics, and strategies of various medieval armies. He covers the rise of the era of heavy calvary, and describes how it was replaced by the English longbow and the Swiss pikeman. His discussion of the various battlefield tactics unique to each army, as illustrated through maps of many of the major battles, proves both informative and entertaining. This is by far the most "readable" and authoritative book on the subject I have read to date.