Warning: Wikipedia contains spoilers
Erhard Seminars Training, or Est, described itself as a psychological and philosophical tool, supposedly based on the works of the philosopher Heidegger, and was started by Werner Erhard, a former Scientologist. The idea of Est is meant to be to break down an individual's personality and rebuild it as part of the group, giving people a new and "better" perspective on life. It is controversial, coming in for criticism from some anti-cult and Christian groups.
Est has officially changed its name to Landmark Education, and it currently promotes itself under this name.
The book purports to represent the experience of the original Est seminars, written by one who went through them. It shows them in a positive light, and describes how the ideas and the training affected the author as he went through the course. A section towards the end of the book discusses the background to some of the ideas in it.