May I ask for the straightforward introduction recommendations in place of GP? I found your comment very interesting -- my understanding of either is still very rough, but as I was reading through Feeling Good[1], I had the feeling that on a practical level, both were attempts at finding out "how to take it as it comes" (excuse the hasty reduction). I did not know of the direct link between them, thanks for that bit of knowledge.

[1]: https://en.wikipedia.org/wiki/Feeling_Good:_The_New_Mood_The...