Sex and Blood Sell, but only in the dark: Why Burnham really ended up in Devil in the White City

Perhaps I am just morbid, but I found myself really liking the parts of Devil in the White City that revolved around Holmes, rather than Burnham. Perhaps this is just my love of fiction, or perhaps I am just some kind of sociopath, but I wanted more on Holmes.
Yes he seduced the women and killed them, and I found this whole thing fascinating. How dumb were these women? How charming and handsome was Holmes? Surely bad people existed in the 19th century- these women must have been instructed by family before leaving home not to talk to strange men. Yet they all went with him by the dozens and perhaps hundreds. Why? I wanted to know more about that, more about the history of the Serial killer, and what if any effect this had on Holmes and the women he targeted.
But instead, I got lots of Burnham. Yes, the feat of putting together the white city was a great one that required men and materials in great numbers. But do we really have to know how many flowers were put where? This, to me, was less interesting than the bloody corpses being shoved into Holmes’s mansion.
Perhaps this just makes me a bad person, or someone who borderlines on the psychotic, but did anyone else think that the book was really about a 100 pages on Holmes that needed to be spruced up with about 450 pages on Burnham in order to make people buy it? I am confident that more people bought this book because of the murders than the fair. Let’s face it, sex and murder sells, and fairs do not. There is only one character on TV that is an architect, and even he spends most of his time trying to get laid.
We in America, however, are afraid of our darker curiosities, and therefore in order to sell this book Larsen needed to add something legitimate. People could claim that they were interested in the architecture, and still get their fill of blood, guts, and sex that Holmes provided.