Devil in the White City, a book by Erik Lawson. I finished that one a few days ago, and I'm about done with The Last Town On Earth by Thomas Mullen. The first is a book that tells two stories; of the World's Fair in Chicago in the late 1800s, and a killer that moved to Chicago a few years before the world's fair and became notorious as a sort of serial killer. The only way the two are related other than temporally is that the world's fair brought the killer more victims.

The second is about a fictional town in the eastern US that tries to cut itself off during the flu outbreak of the early 1900s. It is very well written, but goes through some surprising changes as the town kills to keep people out, but ends up with people being afflicted anyway.