Herrmann Schäfer and his wife traveled to Hunza in 1977. He had to wait more than a month for the permission to travel to Hunza. I traveled to Hunza much more easily in 2019. This book is one of the few available sources about the Hunza Valley. Herrmann Schäfer writes in detail about the history of Hunza, about the people and their ritual, legends and traditions.
(As far as I know the book isn’t available in English.)