Wittgenstein’s diary and secret code writing deserves meticulous study. Gorlée’s book is, to my knowledge, the first comprehensive and methodologically grounded investigation into this subject. The author has looked at every one of the several hundred secret code passages of the Nachlass and produced a book that impressively combines semiotics, cryptography, philosophy, religious and biblical studies, cultural studies and anthropology, biography, musicology and writing research. The book is essential reading for anyone who wants to understand Wittgenstein’s motives for interpolating fragments and reflections from his personal life into his philosophy. The author is to be commended for drawing our attention to these passages and, last but not least, for giving us excellent English translations thereof.