As part of a time-honored tradition going all the way back to when we tried to translate Dalamud (it said ABCDEFGHIABCDEGFGHI), transcribing the text on the demon book was pretty much the first thing I did with that dungeon preview trailer (after geeking out with Rocl and Fusion; feathered ixal!). I won't say that what I got was gibberish, but I've sure yet to make sense of any of it, either.
I swear I can make out several Dravanian words (mor, afah, morn), but the biggest words seem much longer and more complicated than a dragon would use (as far as we've been led to believe), even though the book itself is arguably dragon-sized. I also specifically see "gwyr" and "aen," as in the two parts of the landmark Gwyr-Aen in Coerthas.
The title looks to me: Pentetolothys Athealogicad Ylk'eorz, which I assume to be some pretty warped Greek.
I'll try my best to do a quick pass to give you an idea; but I can't make any promises on accuracy until I really sit down and try to put some polish on the smudgy / blurry bits. It should be enough to give you an idea what it looks like and/or help you get started on your own transcription, though. First impressions, again, I'm thinking Greek + Dravanian might be a good place to start.
Pentetolothys
Athealogicad
Ylk'eorz
Tetheth Cthulaniacl
(probably mistakes here; fades into the brown ink)
Mesca molle nith kol atha
afah on man tha kul ta oka
millh azan thal azan ul
gelli deuz tortil am alli
veuol (cthal?) nk'denil ma
thaeothelphae guil ac'til
paeth byl xun tao (zin djai?)
akh mael (th_the qarnic?)
Mor ann mor silv -------
Morn ynn morn sil ----------
[too much smudging]
ghollill demen ------------
ill fhwil a thac feryne
Cillix yn zolol nedz? sef
tolnysor devid. Molh
holnix xannla tildylt
usen yn vholl thaela
Li Noctologolae netheg
hy?? diem alul morn
unna morn tulwal
mesca molla atymos kol
mor unna mor gwyr
cthol aen dag ? on al
feryne akyn.
Taehlo G?omytoric
[smudged]
[smudged]
[smudged]
Be-e---uin jao azathi ch-------
atymos'ol fhil ambyri -------
Gothin dalam cyllo ud te----