From Time to Time
, by Jack Finney. It is the sequel to Time and Again
. Time travel novels, not using machines and gadgetry, but based on Einstein's theory that other time periods exist alongside ours and we just have to figure out how to move from one to the other. Even though they are fiction, I learned a lot about 1800s New York City from the first one. The first was written in 1970 and the second in 1995, and I thoroughly enjoy both.
P.S. The second one gives us a glimpse of 1912's NYC.