Hard to tell what it is exactly but it looked interesting.
(And, no spoilers.)
I have a few books on riddles and puzzles and they don't seem to be terribly useful.
Riddles tend to break down into a few categories for me:
Category I: Clever Word Play and Puns
These the the Tolkien and historical riddles that tend to either be, an egg, a mirror, my own name, Silence, man (the species), "he was his own father", etc.
I would put the homonyms, pseudonyms, and other word play here.
Fun but limited.
Are the groaners here too?
Category II: Mechanical Puzzles
These tend to be things like crosswords and anagrams. This is the scrabbles and boggles. You get the parts, you mix them up and you get a result.
These are not done much in the RPG world since they are either too long or too short.
This is a shame because these can be solved. And, players feel good about it. I figured out the "W O R D S" is an anagram of SWORD!!!!!! (Take the easy win.)
Category III: Death Traps and Other Contrivances
These tend to be the Esher-esque puzzles of impossible shapes and surfaces. They are a lot of work and hard to solve.
But, the would be in the book of every Delver. Knock out the lynch pin here and the contraption fouls up.
Category IV: Ambitious Puzzles
You don't get enough information at first to solve them (or think you don't) and wait for the last piece to fall in to solve them.
These are the hardest to create, and solve. But can be most satisfying.
What letter is most like Death? "E" because it comes at the end of Life ... but ... should you choose "E" aren't you asking for Death? (Hat Tip to the Batman here.)
A puzzle book that showed a standard way of piecing these things together would have value.