I recently spent 2 weeks in NYC and discovered that they have an entire room devoted to Genealogy. There are many books, folders, and other items that can be accessed there. I don’t live in New York, so I got a free temporary (3-month) card and was off to the races.
Their research catalog is vast and I was able to call up files for various old NY families that my husband is a part of (Pinckneys, Vermilyeas, Tourneurs, Guions, Fourrestiers, etc) as well as books that referenced them. Some were on site and I could get them with a short wait. Some were offsite and I could order them up via the research catalog, and they would be there within a day, maybe two.
What a wonderful resource!