The Gilkey story is an example of a sort of person, usually male, who engages in compulsive book thievery. There are two or three other notorious examples in the 20th century including one who stole primarily from the rare book collections of libraries and had a house full of truly rare items which were just stacked in piles. he had "acquired" them from famous public and university libraries throughout the nation.
Ken Sanders is exactly the sort of meticulous and stubborn person needed to track this sort of behavior over time and distance (he has a tremendous collection of Mormon stuff in his inventory).
As far as the coloring books go, I see a great collecting opportunity for someone with the desire to acquire a wide range of them and the discipline to NEVER color any of them.