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“SLEEP easily, Cyrus, for we are awake,” assured Iran’s last shah, Muhammad-Reza Pahlavi, speaking at the tomb of his imperial ancestor in 1971. This staged event helped forge the myth that the Pahlavis were an adored monarchy stretching back millennia to the Achaemenid empire, a claim to which the shah clung dearly. Yet in less than a decade his embittered people had delivered his throne into the hands of an obscure Shia cleric, Ayatollah Ruhollah Khomeini. James Buchan’s elegant “Days of God”, which came out last November, focused on how all this came to pass. Now Michael Axworthy, a former diplomat and director of the Centre for Persian and Iranian Studies at Exeter University, goes over much of the same ground and explains how the Islamic...