It's not fiction, but definitely horror. The author, Erik Larson, balances two stories: one about the conception and construction of the 1893 World's Fair in Chicago and the other about an opportunistic serial killer who set up a hotel to lure the fair tourists. While it takes a while for the book to gain its momentum, it really is darkly fascinating. I'm halfway done with it now and the level of dread and tension is spectacular.

I'll let you all know how it pans out in the long run...