Peter the great: His Life and world, by Robert K. Massive.New York: Ballantine Books. $9.95.

Described as an "eternal toilet upon the throne of Russia" (Alexander Pushkin), Peter the Great emerges as a man with a single, firm purpose -- to build a modern Russia -- in Massie's comprehensive and thoroughly engaging study. The history of Peter's colorful personal life and reign as czar, with his myriad internal reforms and military exploits, is interwoven with fascinating and detailed disquisitions on such topics as torture in the 17th century, the Muscovite idea of women, and the arduous construction on St. Petersburg. Massie's skillful renderings of personages and events make this era of Russian history come to life.