Helsinki Central Library chosen as the best new public library 7 years ago
The main building at Bryant Park is a research library. It's beautiful - but it doesn't have much circulation, just items of interest for researchers.
The Mid-Manhattan branch is a HUGE circulation library. It's across the street from the main library but confusingly enough - it's in the middle of being renovated so, for now, its colocated in the basement of the main library and a subset of its collection is available. It is _very_ browsable.