Catherine the Great by Robert Massie
She came to Russia at the age of 14 and was promptly married to the heir to the throne, Grand Duke Peter. The purpose was to beget an heir to the throne - promptly. That did not materialize. Peter, who was a real piece of work, did not touch his bride for 17 years. Those years were a period during which she was subjected to much humiliation and disrespect by her strange, child-like husband and his mother, the Empress Elizabeth. Catherine finally was seduced by a courtier and produced a son, Paul - who promptly was accepted as heir to the throne. Elizabeth, happy with an heir at last, then channeled her energy into jealousy of the young couple and especially of Catherine.
When Elizabeth died, the unpopular Peter III ruled very briefly before forces loyal to Catherine rebelled and crowned Catherine as empress. Shortly thereafter, Peter was killed, apparently by overzealous supporters of the new empress. Massie seems to absolve her of any involvement.
Catherine was great. She was highly intelligent and during her long years left to herself, she had read voluminously and made contact with Voltaire, Diderot and many western philosophers and men of letters. Influenced by their culture, she brought Russia into contact with the rest of Europe during a period called The Enlightenment. She was responsible for collecting the fabulous art in Russian museums. She cared about her people and attempted to reform the serfdom system. In this, she was circumvented by the nobility who considered the serfs their property. Practicality induced her to drop the issue or lose her supporters (her 'base' so to speak). Through successful wars and alliances, she vastly increased the land holding of Russia and made it a power to be reckoned with.
Footnote: The serfs of Russia were freed two years before our slaves were freed.
Catherine did have several children by different lovers - or 'favorites' as they were called, a practice almost universal in all the ruling houses of Europe and England, most of whom were male. It always has amused me to reflect that, given the pyramid effect of genealogy, we all are descended from royalty! Think about it....