Monitoring communication, profiling suspicious persons, doxxing one's opponents – long before the arrival of the internet, Europe's kings were already devising sophisticated systems for spying on their subjects. Letters, in particular, were systematically opened and read. A fascinating excursion into the Secret Cipher Chancellery of the Habsburgs, Louis XIV's Black Chamber, and the first era of total surveillance.

Tom Hillenbrand is a German writer. His critically acclaimed scifi thriller "Drohnenland" deals with mass surveillance. His culinary mystery novels revolve around Xavier Kieffer, chef and accidental detective from Luxembourg. Tom's latest book "Der Kaffeedieb" recounts how the Dutch broke the Ottomans' coffee monopoly. The author lives in Munich without any cats.