The classic military history book on battles, in my opinion at least, is John Keegan's The Face of Battle. It's a very in depth look at three battles: Agincourt, Waterloo and the Somme. It's a very readable work and while parts of it may be a bit dated overall it's accurate. It's worth a read if you're interested in a broad look at battles across history.

If you want something more specific Kelly DeVries' Infantry Warfare in the Early Fourteenth Century. DeVries goes into great detail on battles from, surprise surprise, the early Fourteenth Century and documents how warfare was changing at this time.

Take a look at Osprey Books. Most of their books detail the weapons and uniforms of historical armies, but they do publish quite a few books about specific battles.
http://www.ospreypublishing.com