I know that I’m mostly a naysayer on these boards, but I feel the need once again to point out that when I had a brief conversation  with Byron Priess, he basically told me that the clues were only in the images and twelve verses, not in the “supporting” material.
Granted, its been a long time since I spoke with him, but I also think the book says that the clues are entirely within the pictures and those verses.

Well, I bought both a black light and a blue light and tried them.  I have to admit some of the background letters seemed brighter with the blue light, but in general, I could really find no difference with either one.  Certainly nothing new jumped out at me.
wilhouse

For those who do not have the book, let me quote the first color page after the page titled “The Treasure”:
The treasure now,
The story’s told
Set for eternity
In days of old
But Man
His numbers quickly grew
And so the Fair Folk come to you
With their challenge and a pact:
To match twelve verses
With the sight
Of paintings twelve in colorlight.
A pair will lead you to a casque
A little digging is the task
For treasures shining, moonglow, amber,
Emeralds dark and ruby embers.
To find the keys is your reward
For Fairy, peace the real accord.

I’m new to this puzzle as of today, so if I say something that has already been said, I apologize. That being said, I have a thought on how you might link the pictures to the verses. As I don’t have an original copy of the book, my trying this won’t work, so if anyone comes up with anything from this, please post it.—
“To Match Twelve Verses With the Sight
Of paintings Twelve in Colorlight”
With examining the photos as presented in the best quality scans, it looks as if while looking at the pictures (at least most of them), a blue hue can be seen around many of the objects. Looking at this in a BLACKLIGHT (color light) may present something helpful to connect the pictures and the phrases. Thanks

Check the Introduction?