This particular page is reused multiple times throughout the episode. At least part of this has been translated by Starlight, i’ll edit the description…

Let us take a moment to appreciate the sheer effort some animator went to, to cram this page full of stuff that was unlikely to be appreciated.

That page on the left has 6 ‘smaller circles’ surrounding the central circle; definitely representing the 6 Pillars. That triangle in the corner could be mistaken for an Eye of Providence, but I think it’s much more likely that it’s a small pentagram (or perhaps Ponehenge itself) within a triangle within a circle. Perhaps the ‘arrows’ signify that this triangle surrounds Ponehenge?
 
The text below could maybe be translated using prior experience with Written Equestrian (testing it on other things, it works surprisingly well at times), but is likely to be in old ponish - possibly causing issues.
 
The page to the right is fascinating. Ponehenge is clearly visible, along with some (maybe translatable) notes. The boxes towards the middle of the book are strange, but likely just some form of other note.
 
What I find most interesting are the circles - I recognize the moon and a number of constellations being noted, as well as… Could that be the sun and 2 planets? A depiction of Equestria against the sun? There may be text superimposed there…
 
Lastly, the circle in the bottom right… Strange. Used to represent the portal, perhaps? Or yet another planet.