I well and truly don't know for sure. Of course, this goes for anything and RA is no exception.
However I have concrete internal reasoning to believe so. The main thing is that it is written in a very, very different tone to the 99%. What do I mean by this? Well, the quran is written in such a tone, exactly like a maths book. No added BS, nothing missing, straight and to the point, cleanroom detached emotionless language. You can only write with that kind of authority/tone if you have truth on your side. The picture it portrays of civilisations evolving is exceedingly logical - it makes much sense (for spiritual reasons) that evolved civilisations would merge into a single unified mind where nothing is hidden from any part (quranic parallel). The descriptions of densities is superb although it is noted that above 3rd density it isn't majorly verifiable. Despite that, 1st and 2nd and 3rd density are very good descriptions of what is going on, and if this is fictional then the author has done an exceedingly good job of taking the best of spiritual insight and turning it into gobbledegook.
The quran says that to ALLAH is our eventual return, and RA says that 7th density is dissolution into the all (to move into the next "octave" and start afresh at 1st density in that one), these statements are identical.
But the most concrete reasoning depends on the truth of the quran itself - the RA material practically paraphrases quran the whole way through, which a careful read should show you. The "Law of One" and the description of the creator is perfectly in sync with the message of the quran, the same God is described in RA as in the quran. Another reason is personal spiritual insight - many things I have found in RA, I have already been well aware of from quranic study and mind blowing samadhi-type experiences (I get a lot of those, I live a life of bliss these days).
Of course, my stock is 100% on the quran. Reading the RA material has increased my belief in quran 10 fold because it is the first separate source that resonates so well and supports the quranic themes (actually, after a certain point one reaches certainty, not faith). All the prayers in the quran make sense, and RA's perspective is yet another light as to why those prayers are so incredible; after learning about the truth, I would rather be slit a thousand times and waterboarded for a millenium than turn back. And the cherry on top is that RA strictly AND
actively avoids what the quran terms "vain discourse" - all of these things put together lead me to believe that RA, if
not a highly advanced civilisation/being must be a highly spiritually advanced human trying to spread goodly knowledge the best they can, to a certain important crowd that matters the most (those whose minds have been opened to the point of total breakage - the walls have turned inside out & crumbled away). Sometimes the interviewer tries to pry into needless details, each time RA admonishes them.
Judging by your avatar, you will almost surely find the RA material to be an incredibly insightful read. I prefer the llresearch copy of the RA material, it's all condensed into a few volumes (
CLICK ME), it takes something like 2 hours to read if even that and the time will flash if you are anything like me - I was glued to it from the first couple of sentences.
Clearly RA do not know as much about the grand design of the universe as ALLAH (hey, who does!) or do not want to disturb the status quo, judging by the neutrally positive manner they refer to the quran.
I have had my mind opened to things I could never think concievable (think your avatar, but far beyond even what that implies) and RA resonates so well with truth.