There are some good arguments for library consolidation--why can't you take out books from all systems with one card?--among the three systems serving New York City, and there are some arguments against it. 

A recent piece on WNYC, the local National Public Radio station, did a decent job airing the debate, but missed one key element: the role of private fundraising.

Former New York Public Library (NYPL) union head Ray Markey suggested that consolidation would save significantly on management costs as well as combining other operations, helping spare the libraries the annual budget dance in which they appear to face drastic cuts.

Queens Public Library CEO Tom Galante said he was against it, noting that the libraries already get economies of scale on ordering as well as negotiate labor contracts jointly. And he suggested that one large system would mean a greater distance between decision-makers and the patrons they serve. (Indeed, Queens has done well enough for itself, winning the 2009 Gale/LJ Library of the Year award.)

Mayor Mike Bloomberg told his interviewer he'd ask Paul LeClerc, president of the NYPL. And LeClerc said no.

But why? I suspect it's because NYPL, which raises significant funds for its Research Libraries (and, lately, to some extent its Branch Libraries), including from people who want to support "the library in New York," wouldn't want to see two large multi-branch systems, in Queens and in Brooklyn, sharing so much of the wealth. And those running the systems in Brooklyn and Queens wouldn't want to play second fiddle to the larger NYPL.