Thanks for that link to "Journeys into the Bright World", EntheoDjinn, I am in the process of reading it now, it really is pretty fascinating the gradual tightening of Ketamine's insidious grip, literally dragging the authors into the bright depths...
I remember describing to a friend the subtly increasing pull of the 'hole as being "like gravity" in the way that it becomes something of which you are sometimes aware, but which still acts without you always giving it much thought.
I can relate to some of the descriptions, such as the feeling of "fragility" after even relatively small K sessions, like waking reality is just a little bit more oppressive and hard to deal with. Also, while I have never had a daily habit I was involved in a somewhat unhealthy but mercifully quite brief romantic relationship that involved binges of gradually increasing intensity almost every weekend, and although I usually consider myself a rational person, and have no religious leanings, I remember beginning to believe Ketamine was somehow allowing me to glimpse a divine play between forces of good and evil behind the scenes of the universe... in retrospect, I believe this duality was actually a reflection of my own internal conflicted feelings about the relationship and my then partner. I did not do K for a long time following the end of this relationship, and as I mentioned earlier when I did it again recently, these feelings did not recur.
That said, I did also begin to believe that some of the places I visited were actually real places, existing in some parallel reality or time to our corporeal plane... and to be honest, even now, even with full awareness of the effect that drugs can have on our ideas about reality and the likely irrationality of this belief... I still kind of think that maybe they are.
Anyway, coming back to the book, it does seem to me that Marcia Moore might have some traits that predisposed her to being more susceptible to delusions given that prior to this she already held some quite irrational beliefs involving the validity of Astrology and past-life regression techniques. I am not yet certain the fate of Howard as I haven't got that far yet but it does seem at a few points that he has a more rational approach whereas Marcia quickly just throws her higher reasoning faculties out the window. 8)
There are also several points fairly early on which could reliably be considered warning signs, I think, such as her reference to consensus reality as the "charcoal grey world" (Howard on a few occasions tries to dissuade her from using this language, countering that the world we live in is a beautiful one). Also she comes up with this diminutive, unthinking and timid caricature of herself which she calls "Minnie Mouse" or "Worry Wort" and seems to represent the body she inhabits within the aforementioned "charcoal grey world". This is in stark and somewhat bizarre contrast to the beginnings of the egotism that Ketamine is now sometimes known to induce, such as her references to herself as the "fire lady" and the almost hilariously tragic cliche of an Egyptian queen. On that note, although Howard is listed as a co-author so far it really seems like the book is written entirely from Marcia's perspective, in fact even at the points where Howard seems to offer a more rational viewpoint this is basically just ignored.
This is not intended as a slight on the character of either person, in case it sounds like it, obviously we are all hopefully aware of the grip that any mind altering substance can exert over a human being and obviously it is easy to observe the things I mentioned retrospectively, decades later in the Information Age as we are, no doubt it would be orders of magnitude harder to observe these things from within, but these are just my observations so far.