I've been learning about NYC in hopes of becoming a Big Apple Greeter, and have used this library a number of times. My trip late last month was typical.
It has a collection of unique reports, books, periodicals and document about the history of New York City.
They have six public computers with free WIFI access so I didn't have to carry my portable computer. The staff if very helpful, and they very nicely refreshed my memory of how to use microfilm readers.
If you have a special interest in NYC, this is a great place to visit.