Now in paperback, this is a history of an incomparable culture whose influence can still be seen, millennia later, in modern-day Iran and the wider Middle East. During the first and second millennia BCE a swathe of nomadic peoples migrated outward from Central Asia into the Eurasian periphery. One group of these people would find themselves encamped in an unpromising, arid region just south of the Caspian Sea. From these modest and...