On the Shadows of Ideas is a real book, written in 1582 by Giordano Bruno, dedicated to King Henry III of France. It was concerned with his mnemonic techniques, which had so impressed King Henry.
Smallpox was an extremely serious disease that was very common in Elizabethan times. It had very high mortality rates; in 1967 the World Health Organisation estimated that out of the 15 million people who contracted smallpox in that year, 2 million died. It began with a rash, followed by fluid-filled blisters that left survivors with scars, usually on the face (occurring in 65-85% of survivors), and sometimes blindness and limb deformities.
In the Middle Ages smallpox was established in Europe, and by the 16th century it had become very common, especially in disease-ridden London. Even Elizabeth I caught it, but managed to survive with little scarring. After a program of vaccinations in the 19th and 20th centuries, the World Health Organisation was able to declare in 1979 that smallpox is now eradicated from the world.