At Day's Close by Roger Ekirch is a great book about our historical relationship to the night (sleep and not sleeping). http://www.amazon.com/At-Days-Close-Night-Times/dp/039332901...

The Ekirch book referred to is At Day's Close: Night in Times Past [1]. It covers much more than sleep patterns. We think of night as merely the absence of daylight, but in the past it was seen as a different world.

[1] http://www.amazon.com/At-Days-Close-Night-Times/dp/039332901...