Masters of the opium trade: the fabulous wealth of the Sassoons

Just before I started to read this book I had been immersed in the letters written by Jewish merchants based in Cairo from the tenth to the 12th centuries describing the trade they conducted across the Indian Ocean all the way to the Malabar coast. These letters are written in a difficult cursive Hebrew script and in a Judaeo-Arabic dialect, so one needs greater expertise than I possess to read them in the original.