I've skimmed through the resources thread, but there's a notable absence of references to the Persian Empire. I'm sure I can get a little information by checking the Greek resources, since they had this little war thing going on for a while, but does anyone know some good references for the Persian Empire of the 5th and 6th centuries B.C.? (Online would be great -- my local library is pretty limited, as is my money for research books.)

The novel I'm doing the prep work for is less a military action-adventure and more a political thriller/mystery, so accounts of battles, while interesting and their dates and outcomes significant to my plot, aren't what I'm primarily after. Life at court, religious system of the Persians, and political intrigues and tensions of the day would be great. I'm leaning toward setting the piece in the reign of Artaxerxes, mid-400s B.C.

Thanks in advance!