I haven't really started it beyond the beginning of the introduction. I'm intrigued. I'm particularly intrigued to learn that van Schaik worked with Drikung Kyabgon on these texts, and by His Holiness' comment on the cover:
After the Tibetan Emperor Tride Tsutsen (Me Agtsom, 704–55 CE) invited the Zen teacher Moheyan from Dunhuang to Tibet, the Zen teaching was widely spread in Tibet. Jingjue, the student of Xuanze, wrote Record of the Masters and Students of the Laṅka. Although this text, based on a gradual approach to the Zen teachings, was translated into the Tibetan language, the sudden enlightenment teachings of Zen were already widespread in Tibet, and they were the subject of the Samye debate. The Chinese character Zen (禪) has two parts that mean ‘symbolize the single’ or ‘inseparable meaning,’ while the great Kagyu master Phagmodrupa says nonduality is Mahamudra. Therefore, there is no essential difference between Zen, Mahamudra, and Dzogchen teachings.