How the Other Half Lives by Jacob Riis is probably THE saddest and most depressing non-fiction book I have ever read in my entire existence so far. It was published in 1890, and was a first-hand account of the utter squalidness of life in Manhattan's tenement neighborhoods. These days you can't even imagine the concept of ten families living in a single room with no windows or ventilation. But it was indeed a reality. More like a nightmare. There was even a reform movement where it was required that tenements have some sort of light/air source, and the city government actually had to send out people with saws to cut holes in every room in every tenement. Boggles the mind.
I've just cracked Luc Sante's Low Life: Lures and Snares of Old New York, and it seems to be turning out to be a kind of modern rendition of Gangs of New York. It focuses on the decades specifically between 1840 and 1920, and all the city's nasty inhabitants and their places of ill repute. Good times, good times.
While on the topic of NYC history, Gay New York: Gender, Urban Culture, and the Making of the Gay Male World, 1890-1940 (wow, long title) is an interesting read. I don't actually have the book, though. So far I've just read a couple chapters when I have time to kill in the Barnes & Nobles. The information is vast and eye-and-mind-opening, stuff that just makes you go, "Dude, wow." On a readability scale, I think it often crosses the academic-y textbook line. But see, I skimmed through those parts. What interests me more are the personal statements and accounts and articles from that time period.