Highlight the white text inside the block for hints ranging from vague to specific...
These are anagrams of each other.
Hint 2: (this is speculation)
There very well may be more to this.
* It looks like the ovals around the picture may be ambigrammic numbers maybe.
* There are 22 ovals. There are also 22 cards in the major arcana in Tarot. Some of the cards seem like strong candidates, like Procrustes (Too Long Asleep) as the hermit, Marko as hierophant, etc. And Death as the Grim Reaper in Grave Tidings of course. The Major Arcana are the trumps in Tarot.
* The ovals are situated around the center like a clock. Maybe we are dealing with a 22-hour clock?
* The final poem says "...at the end". The instructions for For Want of a Clue say "...and at the end, you will find your hidden means of egress."
* The Theseus guide says that the Gatekeeper gives the Quaices the key to where the Gatekeeper will go next. The Gatekeeper's face is in the middle of each of the bookend poem pages, and he is also in page with the letter.