Quote Originally Posted by athanaric View Post
Try From Cyrus to Alexander. A History of the Persian Empire by Pierre Briant.

Actually this is the reference on Achaemenids. And it's partially digitalized on Google Books if I remember well, but in fact, I couldn't advice you more than to read it from the beginning to the end (it 'll take you some times btw ) . And if you can, burrow The Persian Empire: A Corpus of Sources of the Achaemenid Period from Amélie Kuhrt, which's a perfect compilation of sources on Achaemenids, and in this matter complets Pierre Briant's books.