This isn't really a book for Alexander, but it is a helpful book for Alexander studies because I found myself understanding the historical context of the early fourth century so much better after reading it: Hansen's A War Like No Other : How the Athenians and Spartans Fought the Peloponnesian War (I've reviewed it more fully here.)

As a sidenote, I did find his occasional references to how Phillip and Alexander would learn from and use the facts and mistakes of the War to be rather amusing - "thug" was the kindest word he used for the Macedonian warriors. Why is it that scholars of Greece sneer at the Macedonians, and vice-versa? Oh well, he seldom addresses them directly, and he's excellent on just what the war cost and did to Greece, and that's always an important sub-text for any student of Alexander!

Highly recommended.