"The Varieties of Religious Experience," by William James is one of the "suppressed editions" (banned books) and the book that Trade Minister Tagomi asks the Librarian if he knows. This 1902 book is in the public domain which may be the reason the writers and producers used it. More likely, it is used because it is the classic text on the psychology of religion and might help Tagomi make sense of his meditative vision at the end of season 1.