The opening intro is quite detailed on the history and context (perhaps a bit too long), at the same time it mostly requires some basic orientation in therapy and therapy adjacent issues.
For me personally, the book could be reasonably split into parts inspired mostly by Grof and parts mostly inspired by Frankl (in a very, very simplified dualistic model).
The parts connected to Grof were a good extraction of what is still reasonable there, but my problem with Grof is that well, I do not consider great majority of that reasonable or even meaningful in any way.
On the other hand, the parts focused on logotherapy, integration, specific integration exercises and quite often a very "down to Earth" approach to problems were very good and interesting. At the same time, there is this weird feeling when the author goes through many well grounded exercises and reflections: and than feels the need to talk about mysticism and shamanism for a while in what really feels like a mention that he felt he needed to do, but do not really advance anything.