An extremely readable account of opposites: the architectural designs behind the Chicago World Fair, contrasted with the life of a serial killer, H.H. Holmes, who was operating in the city at the time of the Fair. The link between the two is fairly slim, relying pretty much only on place, but in fairness Larson is concerned more with narrative contrast than deeper connections and it's a tactic that works extremely well. I do think the Fair sections got more attention (and were better researched) than the Holmes sections, but part of that is an unavoidable result of differing levels of evidence - there's so much more for one than the other - and Larson is up front about this, so it grates less than it otherwise would have. But it's really very interesting, and very well-written.