The Devil in the White City is a factual book, based on real events, but Erik Larson writes it more like a work of fiction; ascribing thought and emotion and motivation to people long dead, many of whom would never have had to chance to speak for themselves. At first its a slightly odd way to tell the story; not very "historical" to purists eyes, but humanising and engaging, and it allows him to tell this as a human story, not a dry narrative of events. For both the fleeting grandeur of the Worlds Fair, and the horror of Holmes murders, this human perspective gives the book an enjoyable flavour, for all it's air of slight artificiality.
The first of our two protagonists, Daniel Burnham, was the Chief Architect of the Worlds Fair (also known as the Worlds Columbian Exposition) and the book recounts his early career and then the struggles to get the Fair up and running. The story of the Fair, built in the teeth of an extremely tight deadline and looming financial meltdown is one of determination, audacity and more than a little luck, and Larson makes it feel like a miracle that anything got built at all. He gives a grand feeling of the scale and majesty that the complex must have projected when finished, no mean feat when so few pictures of it survive. There are few on the wikipedia page though, probably the easiest place to get a quick sense of it.
Contrasting with Burnham. Dr H H Holmes was also a man of vision, determination and audacity. By all accounts a charming, intelligent man, self made, a paragon of the age, he was also responsible for the murder of somewhere between 27 and 200 murders of men, (but mostly) women, and children. In an age when shifting you identity was easier, and people lost track of each other all the time, Holmes indulged his urges to kill in a city overrun with transitional visitors. He even had a hotel built - his "murder castle" - designed to facilitate the killings and disposal of remains.
Both men are, of course, impressive in their own way; imposing their will on a world that resists it. Both became celebrities in their time, but both also fell from history; Burnham's neo-classicism was shunned by the next generation of American architects like Frank Lloyd Wright, Holmes, for all the newspaper column inches of his case, is now a footnote in criminal history. Both the White City and the Murder Castle were destroyed by Fire before the dawn of the 20th century. Well, I'm not sure the parallels work out quite as neatly as Larson frames them in the book but it's certainly a neat trick and makes it a gripping read. I don't think you'd any interest in crime or architecture to get a lot from the book!