Peter the Great Revealed
This is the first in the series of three works by Robert Massie detailing the lives of Russian Tsars. It was followed by Nicholas and Alexandra and Catherine the Great. All three of these works are excellent, but Peter the Great is by far the longest and most detailed portrait as Massie takes pains to describe the political, cultural and geographic realiities of the time.
Any student of Russian history, including the most casual, will find themselves happily immersed in Peter's world from the first word to the last.