Creasy's Fifteen Battles; Keegan's Mask of Command

Mask of Command is also very good, especially the chapter on Wellington. I found the chapter on Alexander the Great too unspecific, although that is understandable given the sources. Creasy, on the other hand, is more venerable as an early source of military history than useful or interesting to me now.

On the basis of Mask of Command, I ordered up all of Keegan's book, and I am already half-way through his book on the Iraq war.