Perhaps I read the posts too hurriedly, but I didn't see any mention of the recently published book "Temperament" by Stuart Isacoff. A very readable book, it discusses tuning down through the ages, engaging "such great thinkers as Newton, Kepler, and Descartes as well as musicians, craftsmen, church leaders, and heads of state. At the heart of their dispute is the question of how the tones of a musical scale should be selected."