The most powerful sections of the book

Larson says he tried to recreate the murders plausibly, giving his best guess of how they actually happened. One of the only emotional descriptions in the entire book that was not a quote from someone's overly romantic journal was the description of Holmes's pleasure at feeling the cool chloroform on his fingers. And now that I think about it, the only other description that I can remember is a description of Anna's reaction to being locked in the vault.
When I read the description of the first murder, where Holmes kills the woman with chloroform, I found myself indifferent. She went quickly and probably didn't realize what was happening. I can deal with reading these murders, I told myself. But then when I read about the murder of Anna, I wanted to tear the book up. I felt so bad for Anna. Why did I care so much more about the second murder?
I think hated Anna's murder for several reasons.
1) Anna was just expecting to grab a file, not to be locked in the vault.
2) She was probably in there for a long time, and she was probably terrified the entire time.
3) She didn't go searching for trouble in Chicago like the other girls, she was invited to come.
4) Larson really described her emotional situation, even though he only could speculate.

So for these reasons I really had a hard time getting through the description of Anna's murder. That was when Holmes switched from being a bad guy that I was rooting for to being a bad guy that I wanted to kill.

Another thing that made me very angry was the way Holmes did not send the little girl's letters to her mother.

These were the most powerful sections of the book for me.

Also another lasting impression that the book gave me is the negative view of labor unions. They threatened to stop the fair and only seemed like a bad thing.