"How sad that people ignore the near and search for truth afar."
There are truly meaningful connections that can be made between Reiki and the writings of Zen masters even if you're not a buddhist or a zazen practitioner. This of course is also true of other buddhadharma teachings whether they are from Theravada, Mahayana or Vajrayana. In a way it is common sense as we know that Usui Sensei drew much of his teaching from buddhadharma. Today I would like to recommend the writings of Hakuin Ekaku (1686-1769) also called Hakuin Zenji. His teaching is relevant for Reiki practitioners because it insists on the fact that practice should be accomplished in the midst of daily life and not in retiring to a monastery. Here, people involved in the Gurdjieff work can also find meaningful insights. So if you want some good hints that could potentially enrich and deepen your Reiki practice and understanding, try the Orategama of Hakuin.