You really can't go wrong with Thucydides "The Peloponnisian War." He was there - well he had been exiled just before the war, but it an interesting account. Any library should have it and so will every bookstore. (Anything that has basically been in print for 2300 years can't be all bad)

Generally recognized as the first piece of true history in the west. (Before this we had things like Homer that were less history and more fiction.)

Some of the sections on how the populations of varous outlying islands were subdued are a bit extreme... though memory isn't clear, it has been many years since I read it.

Zendo, you're thinking of Melos, a tiny island in the Aegian. When it refused to join the Athenian League, Athens sent a fleet, slaughtered every man on the island and sold the women and children into slavery.

The Melian dialogue is one of my favorite episodes in The Peleponnesian War. Melos sent a delegation to Athens to argue how silly it was to force a people at sword-point to fight for their "freedom". Every one of the points they made was logical and well argued. The Athenian response to each one was basically, "Well, yes, but if you don't join us, we're going to kill you."

I recall a Greek History survey class in college. When we went over this episode, an Earnest Young Thing leapt to her feet and cried out rage, "But that's so UNFAIR!" The prof, without missing a beat, said, "Sure. But who's going to stop them?"

I also wrote a paper on it in a law school class on rhetoric. My thesis was the limits of rhetorical effectiveness. The prof didn't think it was s'damn funny.

(BTW, I've got three or four different translations of Thucydides at home, starting with Hobbes'.)