The Fall of Atlantis - Marion Zimmer Bradley

For quite some time now I've hoped to find out more about the Atlantean Temple of the One True Light.
I've learnt about this temple via Diana Cooper's work. It is mentioned in at least one of her books and during some of her webinars we travelled back to Atlantis and visited all the temples there, including this one.

The first time I read about it in her book I was in tears before I had what little info there was. I recognised it, I've been there, it was my home for a long time!
I'm not sure in what capacity I served there but I am certain I have been there and worked there.
It was the last temple to remain intact when the dark forces were destroying the rest of Atlantis. I remember me and other trying to hold the Light, to turn the tide, but we failed as the dark had grown too overwhelming as many were involved in it by that time and the Light ones had mostly disappeared.
It is also why in this lifetime I feared doing rituals for a long time. I had this innate sense and fear of "They are stronger than me!!"
Everyone always saying the Light is stronger than the dark, but I'd experienced differently back then. I know in essence it's true, but the Light winning may not be in your lifetime, in other words, it could win way after your demise.
At least that's what I think, based on what happened in Atlantis.
Now it was also meant to happen, but still.

I asked Diana directly if she could do a webinar on this temple, but it has never happened. Maybe it is not her thing, or out of her reach, or too specific for a niche group?

So I was left with what little I did know and had felt. And the craving to know more! Much more!!

Lo' and behold my osteopath advised me to listen to audio books while laying down so I rest my neck & head (neck injury) telling me my body and neck/head really need this. Since I thoroughly dislike lying down during the day, she advised the audio books.
I found one by Marion Zimmer Bradley from the Avalon sequel that I'd read years ago. Almost the entire sequel is in my book case but I became aware there are a few more.
I was looking into this and then came across the book "The Fall of Atlantis" by Marion Zimmer Bradley.
This book deals directly with people who serve in... The One Temple!! I do believe this is The Temple of the One True Light.
The book is part of another sequel Marion had written, but it ties in with the Avalon series and is set before that takes place.
Basically the book "Ancestors of Avalon" -that I have as well- ties the two sequels together.

Now finding that book, as it's out of print... Ifever there are copies they go for insane prices like $197-$500!!! But I found a copy for E20 (same in USD) on Amazon!
Yeehaa!!
I bought it. Couldn't not buy it! This may very well provide the answers and insights I've been looking for for so long!
It won't arrive until mid-September. Not sure why. It's not like it still has to be written,hihi.
But at least it's coming.
I could've gotten an e-book version for E9 but I want a physical version. Some books are to valuable to have as a virtual version and to me this is one of 'em.

Now fingers crossed it does indeed provide answers I'm seeking and so desperately longing to know!
Based on a review I think it does exactly what I'm looking for.
Contrary to what the title suggest it does not deal with the fall of Atlantis. That happens in The Ancestors of Avalon.