Hi Jonathan, and welcome to the discussion board.

The two books can be read in either order. The first (1991) described my own experience of kundalini activation, along with reflection on the significance of the process from physiological, psychological and spirituality perspectives. In later editions, I added on a few appendices that were taken up in more detail in the book you purchased, which was written in 2017, after continuing to live with the process for many more years and dialoguing with many others, some of whom shared their experiences in an appendix. It's a more "intellectual" work, using philosophy and theology to relate kundalini to other kinds of experiences and to clarify its relationship to the Holy Spirit and even demonic influence.

I hope you find the book helpful. Let us know what you think of it.