A history spanning from ancient Mesopotamia, through the Persian, Egyptian, Greek, Roman, and Holy Roman empires. Most of it explores recurrent themes in ancient religions -particularly myths of gods who die and then are reborn, gods sent to Hades (or equivalent) and return, gods who sacrifice themselves in some way, etc. This was groundbreaking stuff, once upon a time, when gods were vengeful and all-powerful. Highlights include the Epic of Gilgamesh, Zoroaster, Baal, Nimrod, and telegraphically Jesus- although it doesn't dwell on him nearly as much as I had expected.
I had expected this to be primarily an exploration about common origins or borrowed ideas in religions originating in the Middle East, but there is a fair amount of straight-up history... particularly as relates to the Greeks resisting incorporation into the Persian empire, and how their unexpected success at this contributed in a large way to the evolution of a "European" culture very different from Oriental (used here in the antiquated sense to mean Turkey, "the Levant", and present-day Iraq and Iran) culture.
The later part of the book makes a case for the Crusades signifying, in a very broad view, a continuation of the Greeks' resistance to the Persians (i.e. Europeans asserting independence or distinction from near-Asian culture... this time to the rapidly-expanding influence of Islam. (Opinions will vary on this interpretation of history, but I'm telling you what's in the book.) The secret orders of the Templars, the Hospitalers, and the Freemasons all find their roots in the Crusades, and became vehicles for an odd mix of social and religious subversion, politicial corruption, and (coming back full circle) cultural dissemination of ancient "dying god" rituals and imagery into the newly branded and newly self-aware "European" culture that developed between the years 700-1500.
The world is a complicated place.