Tanzanite's Castle Full of Books

I'm finishing up a book about the early life of Catherine the Great so she is today's mosaic.    Born into the family of a minor German prince, she was born in 1729 as Sophia Augusta Frederica.  Around 1744 she was betrothed to the heir to the Russian throne, Peter von Hostein-Gottorp (later Peter III) and her name was changed to the more Russian sounding Ekaterina (Catherine).  The pair were married in 1745.  Upon the death of Peter's aunt, the Empress Elizabeth, in 1762, Peter and Catherine came to the throne, but within a few short months, Peter had alienated many powerful groups within Russia and they rebelled.  The result was the deposition of Peter and Catherine being named as the ruler.  Three days later, Peter was dead.  This portrait by Georg Chrisoph Gooth was painted around the time of her wedding.