One aspect of reading old books on virtual reality is the extreme conceptual connection to what is happening in this time in immersive media. Beside the tech aspect that evolved in an somehow unpredictable way the philosophical and base concepts and theories are still valid. This book was written by Claude Cadoz in 1994. He is the founder o ACROE a research lab on new media. His essay of almost 100 pages focuses on the core of VR and future develops. I think it is a book to use when we want to compare the idea of VR we had in the ’90ies and where we are going now when the technology supports all the visions of the first VR explorers.