Farm, Forge and Steam

A Nuts and Bolts Guide to Civilisations

From the introduction:

If you’ve been playing Role Playing Games for any length of time you’ve almost certainly picked up some historical knowledge – most RPGs are, after all, set either in earth’s past history or borrow elements of that history as the basis for much of their setting.

Having at least a passing knowledge of pre-modern societies and cultures, or some aspects of them, is a handy thing – it gives the player an edge and enables the GM to make the game more interesting and believable.