This book was originally written in 1971 and it is doubtful that much has been updated since Tart's original work. Look for yourself. Very few of the references are more recent than 1968-1970. If you are interested in marijuana smokers' personal experience or perceptions in the 1960's, this book is for you.It reflects opinions from the 1960's, not now. Remember though that personal testimony does not prove that the effects came from marijuana. So many other factors could have affected a users perceptions and experience. On the positive side, although it is not a scientific study,it provides good qualitative information from users at that time.