This was a fascinating read. Surprisingly enough, it had little to do with H.H. Holmes' aspect of the book.
I knew of the World's Fair prior to reading this, but it was just the basics of it. Delving further into the makings of it was beyond interesting, and seemed doomed from the start, really. The amount of work that went into it was amazing. As was the pride in it. It's sad that it was marred with such struggle and death. The sheer amount of genius that went into it and eventually came out of it though, awesome. I got to the point with the Fair's story, that Holmes' part in it was kind of on the back burner for me. I think that was primarily because I had already read quite a bit on him, so it wasn't something new for me to focus on.
I was really impressed with Larson's ability to weave these two stories together so fluidly. One would never think that a book about a serial killer and an architect, two men had such huge impact on the country in such vastly different ways, work so well together, but it did. More so with the fact that I'm sure that many people, me included, were drawn to this book because of Holmes' story in it only to get drawn into another aspect of history.
I highly recommend.