Enigmatology is the study and construction of puzzles.

Jeremy Logan, a character who appeared in a minor role in two earlier Child novels, takes center stage here. Logan is a history professor whose speciality is "enigmalogy," the study of puzzling, bizarre, or paranormal events—hauntings, the Loch Ness Monster, etc. (the term appears to be a made-up coinage, a spin-off, perhaps, of the real discipline of enigmatology).

Economics didn't turn out to be exactly the career he had in mind, and neither did law. So Will Shortz turned to enigmatology.