Devil in the White City was a quick read for me, but I know it dragged for many. I was fascinated by the story of the World's Fair. It was really interesting to me. We just don't see things on that scale anymore. The crime drama was secondary to me, but very good.
I just finished Shadow of the Wind by Carlos Ruiz Zafon and I absolutely loved it. It's a little like The Historian by Elizabeth Kostova, which I couldn't put down. It's also a little like 1000 Years of Solitude.