I've been fascinated by the Achaemenids for a long time. By trade I'm a Roman Republic guy and as such I have learnt a lot about Parthia and Rome's struggles with them, but the great Achaemenid predecessor is somewhat of a mystery to me. Would very much value any pointers as to where I can learn more about them. Thanks!
This is my time to shine!
For military history, I would recommend Shadows in the Desert, by Kaveh Farrokh:
http://www.amazon.com/Shadows-Desert-Ancient-General-Military/dp/1846031087
Whilst he does utilize ancient Greek Sources, he also makes it a point of referring to archaeological and pictorial evidence from Persia itself, such as the surviving bas-reliefs as Persepolis. He is also fairly balanced in that he objectively describes both the strengths and weaknesses of the Achaemenid army, especially in regards to Greece. Whilst he does advocate the idea that Indo-Europeans originated in the middle-east (which has been disproven with the confirmation that the Yamna Culture as the source of the original migration, I believe), in all other areas he is quite accurate.
Another book in relation to Persian military history is the Achaemenid Persian Army, by Duncan Head. It was published by Montvert, a company that is now out of business, so there are no copyright issues from reading it online here:
In regards to a general political, economic, legal and social examination of the empire, I would suggest Ancient Persia: A Concise History of the Achaemenid Empire, 550-330 B, by Matt Waters:
I similarly have that book and I can assure you it is incredibly informative and very well written, and makes use of a wide range of primary courses from the Iraq/Iran region rather than just relying on Greek authors.