Tycho and Kepler Ferguson, K.
This is an amazing book I read several years ago about two giants in the history of science. Many are aware of these two individuals, but I would hazard a guess that few are aware of the fascinating tale of their lives, the dedication involved in noting countless naked eye observations of the movements of the celestial bodies and the genius involved in unraveling the true motions contained within the data.
This was a book that I read slowly because I simply did not want it to end. It was that good.