I seem to recall listening to this 9 hour recording earlier this year in 15 minute chunks on Youtube before losing the plot line one too many times, due to occasional nodding off. Eventually I downloaded the pdf book off the net and read it to fill in the gaps I had no chance of identifying.
It's very much about the young McKenna but between him and his brother Denis they experience something I don't think anyone else has described elsewhere though I have heard William Henry talk about the glowing blue electrolytic skin effect that Terence experienced during a sexual encounter he had on this trip. So there's a comparative mythology Stargate episode here but other than that it's unique and very possibly important though Dennis prefers to downplay the episode he is in some chapters the star of the story.
I've written more about it back here.