Cool book, but a little odd.
It's sort of a puzzle-type book, like those movies with Nicholas Cage searching for clues, et cetera. But quirkier.
However, if you like them, a better puzzle book is "The Rule of Four" by Ian Caldwell and Dustin Thomason.
I recently saw a lady at the park reading something else by one of these authors and eagerly wrote down the title to read later.
She probably thought I was crazy.